You should take into account the lights intensity and distance, as well as the reflectivity of the material.
I managed to achieve very close match when disabling the mirror and playing with the light.
Unfortunately that was made in 2.49, and the same file rendered in 2.5 gives different result.
This may not satisfy your particular needs, but in my mind a perfectly acceptable solution is to tweak the colors in the compositor with an RGB node. You could use IDs to isolate the objects with the paint values and color correct them in post.
My idea would be, although i still didn’t fully understand this linear workflow, that your input color is wrong due to your rendering being in linear space and your color is still in srgb space. It could be that you need your color to compensate for the gamma correction in your rendering. Try adjusting your color to something like:
0.168627^2.2 / 0.172549^2.2 / 0.486275^2.2 = 0.0199177 / 0.0209511 / 0.2047105
0.4^2.2 / 0.509804^2.2 / 0.356863^2.2 = 0.1332085 / 0.2271366 / 0.103634
just put them in a test material with diffuse intensity 1.0 and at least the material preview looks more like the color you want
I should not recalculate colors manually
or i am not understanding the figure
the color picker do not recalculate colors, but blender display “linear color”.
It would be better - if i could choose normal RGB-color and blender convert it to linear when render
oh i understand it now:
The new convention in Blender is to store colors internally in a linear color space, similar to other applications like Nuke that support linear workflow internally. The exact values that you see in this case are the linear numbers
blenders renderer and the color picker both work in linear color space, so that WYSIWYG. Your color was a sRGB color, and the sRGB colorspace has gamma applied. as far as i understand it thats why you need to recalculate your color value. Imo that makes perfect sense. Maybe it would be cool if the color picker had a flag where you could change the space in which you’d like to specify your color.
You could also input your color through the node editor and put a math/gamma node inbetween your colors/textures. This way you’d have perfect control over everything and wouldn’t have to recalculate it.