No, in general they mean nothing. It is kind of a means for branding. So TP for example is known for his "grey tops", as they always test good. They are literally called "the grey top" and offered in boxes/labels that are branded "the grey top". So if one were to see GH on the market called "grey tops" and assume automatically they are good, because TP's are good, then they could be in for a rude awakening.
However there are reliable blues that test just as good, and consistent as his Greys. Then there are greys that are on some of these Powder source lists that are completely fake. Really there is no comparing across colors.
To take your test cyp comparison. Lets imagine test cyp had no labels. It was just vials with a top color. Billy Bob labs has some cyp in vials with red tops, that is always testing good. It has tested good for years. No slipping in quality. Now all of a sudden 15 other labs start offering "red top cyp" to ride Billy Bobs reputation. Maybe some of these labs also have red top cyp that is good, and sometimes it is underdosed or fake.
It all comes down to who has it. There are very few people in the generic game, worth even gambling on.