Yeah they should have had black as 5.x, grey as 6.x, white as 7.x, green as 8.x, and gold as 9.x
Or just use the Blizzard/rpg rarity colors for user defined groupings so that people can make their own thresholds for how to opine for whatever ratings.
For example, I typically think of each number as three categories: low-7s, mid 7s, and high 7s. A low 7 is watchable and decent, a mid 7 may be pretty good but not have a ton of truly moving content or messaging, and high 7s are like the last rating of ultimate popcorn - fantastic, but relatively intellectually empty. And as soon as you hit 8.0, to get there, it has to start having some levels of boundary-pushing of my expectations AND be very good.
So I would relate all of the 7s as like a Diablo green item rarity, maybe with high 7s being blues. High 8s maybe starts to get into yellows, and 9s are legendaries with mid and high 9s being reds or like Diablo ancients. Very low 7s and high 6s would definitely be whites, with mid and low 6s being greys. And anything under there... Probably also greys? Maybe have a gradient where the lower the rating, the more transparent it gets. 1.0 or 0.0 (whatever the lowest is) would have to still be visible, though.
It shows the trend but the colors make this look far more severe than the scores reflect
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