When filling graphic primitives function glColor3ub(80, 0, 0), some pixels inside the figure obtained colored a little differently than I need, for example, color of these pixels is - (72,0,0), (88, 0, 0), (89,0,0).
What do I need to do to figure was covered with a solid color?
(Version OpenGL 3.0)
You need to figure out why the pixel colour isn’t being set exactly to the current colour.
Possible reasons include lighting, blending and multi-sampling. The last one should only affect pixels where the ownership, depth, stencil and scissor tests pass for some samples and fail for others. And anything which is done by a shader (you don’t mention whether you’re using a shaders, but glColor() isn’t widely used with shaders).
What’s slightly odd is that your reported values have red components which are both higher and lower than the current colour, but the green and blue components are always zero. That isn’t a symptom of any of the most common situations.