A Simple Guide to Digital Colour

Using an older ink drawing of an octopus, I’m going to be running through the basics of how to apply digital colour to an image in an easy way for beginners. I’m not including any advanced techniques just the basics of colouring a black and white drawing. It doesn’t matter if this drawing was done traditionally and scanned in or of it was done digitally.

In terms of software applications, I’m using a mixture of Photoshop 6.0 and the Android app Autodesk Sketchbook. However the tools and basic techniques I’ll use here should be available in almost all digital art applications and the names of these tools are fairly consistent across all platforms too.

Below is the image I’m going to add colour to. It’s one of the black and white ink drawings of an octopus I made a month or so ago.

I used a camera to photograph my traditional ink drawing and then loaded it up into the computer. Sometimes I scan a drawing in too. Once I had it uploaded I cropped the drawing and then transferred it to my tablet so I could load it into Autodesk Sketchbook. Below, you can see it loaded up in the Sketchbook program.

Using blending modes to see your line art over the top of your colour

The first issue beginners get when adding colour to a black and white drawing is how to colour the picture without painting over the drawing. To do this we use the layer blending modes which are present in almost all digital art applications.

To do this in Sketchbook I clicked the layer with my line art on it…

Then I clicked the part of the menu which was about blending modes…

This brought up a list of layer blending options. Then I chose “Multiply”, like this…

Once I’d done that any colour I put in the layer below the octopus would show through the line art. I could then colour the drawing without touching the line work…

Masking with flats

The next thing I do for most digital drawings is to create what is called a flat layer. This is where you draw flat colours (just plain 100% colour) onto a new layer of your digital drawing. You can later use these flat colours to quickly select different areas. In a more complex design you might have many different colours and tones of flats to set up so you can colour lots of different parts of your drawing easily and seperately, but in this design I just want to be able to distinguish between the octopus and her background, so I just drew some flat colour over my octopus like this…

If you look at the flat colour I added without the line work showing it looks like this – below. (This was my first pass. You can see how I needed to tidy it up and make it much tighter.)

Once the flat layer was done I pulled it out of the way to the bottom of my set of layers as it was really just a tool to help me quickly select things. It wasn’t ever going to be a layer which would appear in my final image. In many ways it’s exactly the same as an air-brush artist cutting out a masking sheet to allow them to colour one bit of the painting and not another.

Colouring using my flats

Once I’d completed this flat layer I could then easily select my octopus using what is usually called the magic wand tool. This tool will select all of a particular colour range or tonal range on your picture. Here I used just one single flat colour with no variation in it. The magic wand tool finds this really easy to select. So I clicked on my flats layer and clicked on the octopus and the magic wand tool selected the octopus for me.

With the octopus shape selected I could then colour the octopus using the air brush tool without going over the edge of the animal. In this way I could apply a range of colours in a gradient like this really easily…

Colouring using layers

Next I wanted to put in some background. For this I made a new layer below my octopus ink layer, and my octopus colour layer and then painted over it again using the spray paint tool. Because it’s a background and I want my octopus to “pop” off the page I used, on average, a lower saturation and darker tone for this. Our eyes are drawn to things which are more saturated and have more contrast. So making my octopus lighter than her background and more saturated really helped.

I thought this looked a bit dull though, so I used a spotted brush to add some texture to the background as if rolling breakers were crashing above our scene causing foam to appear in the water. I put this these textural marks on a seperate layer…

Once this was done I used the pen tool to draw in some colour for some of the details, like the octopuses eye and the lumps on her mantle. I used another new layer to do this. By keeping my layers seperate I could then alter things later really easily if I wanted to make changes. As it happened on in this picture I later realised that I hadn’t coloured my octopuses suckers. I could then go back and add the sucker colour to this layer with all of the other details on it. Because I kept it seperate if I made a mistake while painting this addition I could easily erase and refine it.

Specular highlights and other “wet” effects

My next job was quite subtle. I wanted to give the viewer the feeling that the octopus was wet. So I added what are called “specular highlights“. These are sharp bright white patches where light is directly reflected off of the octopuses wet body. I’ve put a big one on her mantle and some thinner linear highlights on her arms. You wouldn’t actually see this on an octopus under the water since the reflection happens because of the air-water interface on wet surfaces, but giving my viewers the right impression helps draw them into the illusion of a wet subject.

Then, to encourage the viewer to see the background as water too I also added some circles for bubbles. Now in a natural environment, without a diver present, there aren’t always any bubbles to be seen, but I think they help sell the image so I put them in anyway. Finally I made my correction to the suckers as well to add more interest to the picture.

Final adjustments

My final job was to bring the image into Photoshop (or I could have used another digital art package, like Clip Studio Paint or Affinity Photo) and adjust my colours and levels. I do this in Photoshop because the Photoshop tools for this are much more accurate and effective than the free app Autodesk Sketchbook. Here I wanted to make sure that I’d got some good bright highlights, some nice dark shadows and colours that worked well for the feel I was going for.

Colour modes

If I were going to print the image I would then change the “mode” of the picture from RGB, which I normally work in, to CMYK, which adjusts the picture colours for printing. Since this image is for here on the web, RGB will be perfect, so I didn’t change to CMYK.

If you do want to print a colour image all you have to do is set the image mode to CMYK. Sometimes there are several CMYK options to choose from and which one you use depends on your printer. But any CMYK mode will help your printer print an image with better colour.

What happens when you switch to CMYK mode is that the image’s colour will seem to change a bit. What the computer is doing is showing you how the image will look when you print. If you don’t like the changes it has made then you can adjust the colour hue (red, yellow green blue etc) and the saturation to get the image how you would like it. Don’t be afraid to play around with the colour to see what it can do and what you prefer. Just use the undo button if you don’t like your changes.

(Managing colour is actually a very complex issue which also involves the colour characteristics of your computer monitor as well as your printer. Humans also see colours differently from person to person. I’m not going to go into any detail on this topic here as it’s quite advanced and involves understanding colour spaces and how to manage them. The only concept you need from here is that it helps to use CMYK for printing and RGB for the web.)

Here is my final RGB coloured image…

That’s all for now. I hope this was helpful.

If anyone has a go at using this guide and makes some artwork I would absolutely love to see it! You can always link it in the comments if you decided to have a go. I would also be happy to include a link to your artwork here on this post if you would like to share it like that.


9 thoughts on “A Simple Guide to Digital Colour

  1. I’ll be sure to keep you in my prayers as well as to send all the positive vibes I have your way that all goes well in October. I have struggled a lot with pandemic teaching and there have been times I’ve contemplated a career change, but it would have to be so hard to not be able to be in my classroom for reasons beyond my control. My heart is with you in all of this. You have such a gift as a teacher and I see it all the time in your writing. I can only imagine how amazing it is to be in your class!

    Liked by 1 person

  2. Thank you! You’re words about my teaching mean a huge amount to me. I really miss it, especially at this time of year. I have a pain clinic appointment in October so I am hoping they can help me so I could get back into the classroom.

    Liked by 1 person

  3. It is so obvious you teach and I love that! I don’t have any talent in this field at all…no, wait. Let me reframe that. I’m not very comfortable with creating art like this as I don’t really ever practice or do it nor do I have any formal training. But as I read this it was all so clear to me. So my teacher part came out and felt all warm and fuzzy and appreciative toward your teacher part. As always, this is such a gorgeous piece!

    Liked by 1 person

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