Yes Steve as usual it was an interesting question from MAJWIZ
Re: RGB
As stated Black is RGB(0,0,0) and White is RGB(255,255,255)
Gray tones are numbers between these values and are made using similar number sets like this - RGB(25,25,25) - RGB(128,128,128) etc...
Colours are made with dissimilar numbers like this - RGB(25,35,46) - RGB(128,137,148) etc...
To simplify things I usually set the fog etc in the editor and use overcast to vary the ambience.
Example:
if ssnarea(player,1) and never() then
overcast(50,100)
endif
Where 50 represents units of overcast intensity and 100 represents units of change over time.
EDIT:
BTW - If you want natural looking water use 99,99,99 in the water settings for your map.