I get lots of questions about how to paint this color or that color on a model. In my reply, I always end up trying to explain why a particular color is "easy" or "hard" to paint in the process. I've decided to try and explain why some colors are harder to paint than others in the way that I think about it.
Now I'm not sure that harder is the word either. It might be more of a case of certain colors requiring a different approach. One that is not often done and that is seen as being "harder" to do.
So let's get into the explanation then.
I chose my Pre-Heresy World Eater model there because he includes colors that are perceived as both hard to paint and easy to paint. He's got white which can be tough and requires a particular approach and blue which is often seen as easy and uses another approach.
From here on out though, we are going to remove the hue (red, yellow, green, blue, etc.) and only be dealing with values (the degree of light or dark as compared to something else). Every color, if you remove the hue, has a value. Here's what I mean. No matter what color you take, you can remove the hue and look at it as a shade of grey and determine what it's value is.
Once we know that all colors have a value relative to what's around them, let's look at why some values are harder to paint and make them appear as though they have dimension and aren't just flat.
We'll use this box as our example. If we paint it our base color (B) on all of the sides, it appears flat. We need to add some shading and a highlight in order to make it look like it's a shape (box) and it has dimension.
And here's our dimensional box. Our base color (B), our shade (S) and our highlight (H) all work together to give us the impression that the object in front of us is under a light source and actually has a shape to it. Our base is one value, our highlight is slightly lighter than that and our shade value is slightly darker than our original base color.
Ultimately you can do more than one highlight or shade, but we're going to keep it simple for the discussion today.
So why are some colors harder to paint?
Because of their value. Depending on where a color falls on the scale when you convert it to a value will determine what other values you have to work with for your shading and highlighting.
Look at our middle base (B) example. Since it falls in the middle of the value range, we have room on both sides for a shade and a highlight value. It's very easy to make this value (color) appear to have dimension.
If we look at our far right base example (black), we have no room to shade it. We are going to have to rely on highlighting alone to give the piece dimension. This can be tough because highlighting can be done by drybrushing (which can often be messy) or line highlighting which can be tedious and time consuming.
So how do people solve painting black? Sometimes they use a very dark grey for the base and move back towards the middle of the grey scale slightly so they now have room for a shadow to help define the shape in addition to the highlight.
If we look at our far left base example (white), we have no room to highlight it. We are going to have to rely on shading alone to give the piece dimension. This can be tough since most of our shading is done with washes and such and unless we are very careful in their application, they can quickly darken down the whole piece and we no longer have the light base color we want.
And how do folks solve painting white? Sometimes they use a very light grey for the base and move towards the middle of the grey scale slightly so they now have room for a highlight to help define the shape in addition to the shadow they already have.
Figure out the value and see where you can go
Next time you look at a color, think about its value. Do you have room on both sides of it for your highlights and shading? The answer will almost always be yes. It's not until you get closer to the ends of the spectrum that your options start to dwindle down and you need to start looking around for solutions.
Colors (values) at the ends of the spectrum aren't impossible to paint, you just need to think about them first. Now there are a few other factors to consider as well like the transparency of your color and how many coats it's going to take to get a consistent finished coat (remember Foundation paints?). Another thing to keep in mind is primer color. Try and match it's value to your base color value so it doesn't alter your base color or make it so you need to do a million coats to cover it.
Make sure to check out these posts as they might help:
The trick to painting black is in the details
There are only two ways I paint white