The basic form of the Wilbur shader is
Code:
ColorAlt = RGB(0,0,0)
ColorLat = RGB(0,0,0)
// other shader initialization goes here
if (altitude > sea level)
if (CoeffAlt > 0)
// calculate altitude color for land
endif
if (CoeffLat > 0)
// calculate latitude color for land
endif
// calculations for other land colors
else
if (CoeffAlt > 0)
// calculate altitude color for sea
endif
if (CoeffLat > 0)
// calculate latitude color for sea
endif
// calculations for other sea colors
end if
FinalColor = ColorAlt*CoeffAlt + ColorLat*CoeffLat // + contributions from other parts
The default value for a color in the shader is black (RGB(0,0,0)). If a shader computation doesn't create a value, then the default value of black is used. In the case where latitude colors for sea are computed, the non-ice color is left to the default. That's where the black comes from, the default value. In your particular case, the light blue-gray is averaged with the black of the default color and you get a dark color. Because of how the RGB color space works (and your computer's video system hardware and your own eyeballs), there isn't a linear relationship between RGB color and perceived color.