When it comes to basing, we usually think about what kind of theme we want, but often forget about taking that theme and applying color to it as it relates to our model.
I got this very question the other day and thought I might go into the things I consider when basing a model. Most of the time, I know what theme I want from the beginning. We all have our favorites. Mine is the urban look as though your force is pushing through a destroyed city. But then there is the question of what color to use.
I have two major approaches
I have two basic approaches when it comes to picking colors (or values at least) for my bases. Both of them play on contrast and are designed to make the model stand out from the base and pop on the table.
Here's a closer look at this guy.
The first approach is the dark model on a light base
If my model has a dark color scheme as this Iron Hands marine does, I will usually go with a light colored base to make him stand out. The weathering on the lower portion of the model is designed to tie both the model and the base together, but he still stands out as a dark shape on a light base.
The second approach is the light model on a dark base
The very same thing as the first approach except you flip the light and dark. In this case, I have a light colored model I want to make stand out so I do the base a dark color.
Beyond value, using color to separate model and base
You can also use contrasting colors (blue model on an orange base from example) to help make your model stand out.
By taking a little bit of the contrasting color (compared to the predominant color on your model) and incorporating that into your base, you can help set the model apart from the base. And don't feel like it has to be obvious. Just because your Blood Angel is red doesn't mean your base has to be green. You can add a slight hint of green to help get the effect.
What about making your model blend into your base?
Not everyone wants to stand out on the battlefield. While marines may not use camouflage extensively, other armies do. In the case where you want your model to match your base, it's as simple as using similar if not the same colors on both the model and the base.
Since this guy is wearing camouflage painted armour, it wouldn't make any sense if the pattern on his armour was different than the base he was standing on. I used the same colors on the base as I did on the armour so he would "blend in."
You can do something similar by putting a dark model on a dark base or a light model on a light base. Instead of standing out due to a value contrast, your model will blend into his environment a little more.
This means I could take my Iron Hand marine up there and put him on a both a light or dark colored base. Both would work just fine. The light base (since he is dark) would make him stand out. Putting him on a dark base would make him blend in a little more.
There are other ways to tie your model and base together
Looking back at the Iron Hands marine, the weathering on the lower portion of the model is designed to tie both the model and the base together. Whether you do it with powders, washes or drybrushing, taking the few extra minutes to tie your model to the base can really change the look of your army overall.
It doesn't have to be over the top either. You don't have to do crazy mud caked up on the lower half of the model or enough dust to cover the original paint scheme. A subtle shading/highlighting effect can do wonders to bring both parts together as one piece.
In this case here, I used the basecoat of this model to tie the whole thing together. If you look carefully, you can see both the model and base are basecoated with a reddish-brown color. Having the reddish-brown color show through on the model and the edge of the base ties the whole thing together as one.
Putting it all together
Let's look at an example to show how it all comes together. We'll use my pretend Ultramarine model here as our test subject.
Since he's sporting dark blue armour and I want to do an urban style theme, let's look at some of my options. Across the top row, we have the light and dark options going with a basic grey color. The light grey color offers a little more contrast than the dark grey color. Since I like dark colored models, I'm going to opt for the dark grey though.
Across the bottom row, we have our same Ultramarine on a contrasting color base (orangish-brown color). We have two options of light and dark again as well depending on how much we want our figure to stand out.
Sticking with my dark look, I'm going to take the features I like from both rows of base options and go with a dark orangish-grey color base. The dark color of the base will tie in with the model and give me the overall dark look I like and the addition of the orangish-brown color will give me just a bit of contrast and separate the mode from the base.
Make sure to check out these posts as they might help:
Basing with free materials found around your home
How to apply static grass so it stands upright