Question how light works in Oolite.
According to Planetinfo.plist page on EliteWiki sun color is blended with 50% white so it will never be a saturated color. Indeed, generating sun_color = "0.999 0.000 0.000 1"; (saturated red) and taking screenshot I got RGB color of solar disk 255, 170, 170 or HSB color 0, 33, 100.
Is this color blending implemented to illumination effect too? What color will be white sheet of material illuminated with such sun? The same RGB 255, 170, 170?
Seems color blending effect must be taking into account to simulate sun colors based on real astrometric data.
The quick answer is yes, but let me explain a bit what happens.
The sun color is calculated with some white blending in it. The calculation is a bit more complex than just adding 50% white in; there is some hue and saturation manipulation going on, as well as an initial pre-mix with 30% white and if you want to see exactly what happens, you can refer to the OOSunEntity.m setSunColor method in the source code. Anyways, the sun color that gets calculated is then fed to the OpenGL system as follows:
Sun color after blending with white is set as the OpenGL light source 1 diffuse color.
Sun color exactly as originally requested (in your case (0.999,0.0,0.0,1.0)) is set as the OpenGL light source 1 specular color. This gets mixed with the material's own specular color to determine what color the final specular highlights will be.
To answer your question in a more practical way (and keep posting screenies in the screenshots topic), I did the experiment you described. I took a metal alloy model which looks like a very thick sheet of paper and changed its material properties to make it something close to paper. Set specular color to (0.2,0.2,0.2), gloss to 0.2 and gave it a diffuse color of (0.76, 0.76, 0.76) because in nature nothing has really a diffuse color equal to pure white and even that 0.76 is close to the value for the color of snow, so I am actually exaggerating it. Then set the sun color to redColor and blueColor and took a couple of shots from different angles for each color. Here it is:
and, from a more lit angle: