The "color-mask" textures here are used by the game to tint the icons based on a player's color and highlight-color.  The red channel in the mask controls how much of the main color is present and the green channel controls highlight-color presence.  Here's how to recreate the same effect in photoshop:

1)  In the main icon image, go to Layer->New Fill Layer (Solid Color).  Pick whatever color you'd like and set the layer's blending mode to "multiply".  Make sure this layer is above the other layers.  You should now see the entire image tinted in this color.

2)  Open the color mask image, go to 'channels', and select the red channel.  Now select all and hit 'copy'.

3)  Back in the main image, option(alt)-click the mask icon for your new color layer (the white square to the right of the color square).  This should let you edit the mask for that layer and you should see an all-white image.

4)  Now paste the red channel that you copied into here. (it should show up as greyscale). You may need to resize it if the mask was a different resolution than the icon.  Click on a regular color layer to exit mask mode and you should see the color is now applied only to certain areas of the icon.

5)  Repeat the same steps to create a highlight color layer; just pick a different color and use the green channel from the mask image instead of the red one.