The colors are either full red, full green, or full blue. This is what it looks like:
To me it really looks like green is more bright, then red, and blue is almost not bright at all. Is that just a visual artifact of human perceptions or is there something i did wrong?
Or is there some trick to compensate for this difference so that all colors will look equally bright and glowing?
This is the way color works. Red, Green, and Blue all operate on different wavelengths to how these colors are absorbed. Even though they are the same power level, green will appear brighter.
If you’re interested in more in-depth information try searching Google to explain why green is brighter to get started.