I decided to post a "down and dirty" tutorial for adding team-color using only Paint.NET. I use this software for the bulk of my work because I have no need to buy Photoshop and GIMP takes too much time and is too complicated for my needs with most of my modifications, which consist of simple re-skins and such.
Paint.NET is very basic software, so you may not get the professional results that Nutty can using Photoshop, but I can do a team-color of a file in about 2 minutes using Paint.NET and the results are good enough for me. Unlike GIMP, you don't even need a .dds plug-in to use it. If you are interested, you can
get Paint.NET here.
OK, so my brief tutorial. I will be using the Mindflayer unit and changing the orange parts of its outfit to team-color:
1. Open the .dds file in Paint.NET.
2. Add a new layer (if the Layers palette is not open press F7). A new layer called "Layer 2" will appear above the Background layer.
3. OK, this is the critical part: In the Layers palette, double-click on Layer 2 to open the Layer Properties dialogue. At the bottom of the dialogue box is an Opacity: textbox and slider, which can adjust from 0 (full transparency) to 255 (full opacity). The default is 255 and we want to set it anywhere from about 40-100, depending on how light (bright) our selection will be. If it is white, 100 is fine; if it is very dark or almost black, set it to 40 (or possibly less depending upon your preference). The orange parts of the Mindflayer unit are varying shades but is relatively bright, so I will set the opacity to 80 for this tutorial.
4. The Layer 2 settings are now set to the desired opacity, so now click on the Background layer to begin selecting the areas to team-color. The current layer (Background) is now highlighted in blue.
5. From the Tools palette (Press F5 if it is not visible) there are three Select tools: Rectangle, Lasso, and Ellipse. You can use any combination of these to create your selection; select one then click, hold-down, and drag the cursor to the desired shape. Hold the Ctrl key to add more areas to your selection.
6. Once you have finished with your selection, use Ctrl+X to cut the selection from the Background layer. Now select Layer 2 from the Layers palette and use Ctrl+V to paste it into Layer 2.
7. Now we need to convert the selection that we pasted into Layer 2 to be Black+White (Grayscale). Use Ctrl+Shift+G to change the selection on Layer 2 to grayscale. Now, save the file to the Paint.net default .pdn file format. You do this in the event that we wish to increase/decrease the opacity if the results in the game are not what you wanted; the .pdn retains layer data but the .dds file will not.
8. You are done, that was easy! Now save the file as a .dds by using Ctrl+Shift+S, browse to the desired save location, selecting DirectDraw Surface (DDS) (*.dds) from the Save as type: pulldown, entering your desired file name, then clicking Save.
9. You want to save the file as a DXT3 (Explicit Alpha) .dds file, so ensure that it is selected from the Save Configuration dialogue and click OK. It will now notify you that the format does not allow layer data and must flatten the image; that is OK, so select Flatten.
10. Here are the results of the Mindflayer in the game using a civilization whose team-color is green. You will note that the striping details on the hood aren't very clear because the team-color floods the details somewhat when using a basic method such as this. I might be able to minimize the effect somewhat by increasing the opacity a bit, but for the most part the unit looks fine to me at the scale that it will be in game. A dramatic improvement for only 2 minutes of time!
NOTES: You may wish to create additional layers if you have desired selections to team-color with dramatically different lightness/brightness. Put the darker parts of your selection on a layer with lower opacity and the lighter parts of your selection on another layer with higher opacity. Follow the rest of the tutorial per usual. Also, if using an SREF (Specular Reflection) file, make sure that the areas that will be using team-color on your DIFF file (Diffuse, i.e., what you just edited) have the corresponding areas on the SREF file as solid black. Otherwise, it will interfere with the transparency of the team-color.
Hope this helps!