The colors that the firework star textures use are based on the pre-1.12 color scheme, the screenshots only show yellow, light blue, and cyan as they are the most obvious ones but all colors are affected
Attached are 2 screenshots which compare some of the firework stars with other items in 1.11.2 and in the latest snapshot
To fix this the firework stars could use the same colors that the dyes use rather than having their own color in the code
Fixed Textures (from Bedrock Edition)