I have an idea for a map that I'd like to make (if I can find time to learn to do it after work, wife, baby, house, and dog... LOL). But I'm wondering if it's possible to alter the color and maybe the opacity of water.

Yes.

In order to change colour you need to ammend the following settings to the Effect("Water") section in your fx file:

RefractionColor(28, 67, 84, 128);
ReflectionColor(28, 67, 84, 128);
UnderwaterColor(28, 67, 84, 128);

the numbers indicate the Red Green and Blue settings the fourth number represents the Alpha (basically the opacity in this case) setting. Under water colour setting is obvious and you'll probably want to tinker a bit with the others to get the exact effect you want. Hope that helps.

Very concise, Kyross! And thanks, Carbine, that's what I needed to know. Although another thread today leads me to believe that others have already been working on my idea.

If you have any other questions about modding I'll try and answer with the solution included. xd

LOL. Thanks, I'd appreciate that.