These are the comments from the question What is “relatively uniform resonant frequency”?. I'm pretty sure that the colors are different, maybe their brightness. Is this normal?
I use Windows 7, with updated Firefox. I do install the Stack Overflow Extras (SOX) script, but there is no option in it allow changing the comments' color. I notice that this is universal, every section of comments in every question or answer in every Stack Exchange site has this behavior.