After [this PR](https://github.com/ManiVaultStudio/Scatterplot/commit/227f92f4d869fc509948bb33230a4f3a1c0967ef), an opacity dataset cannot be used for a subset position data, while a color dataset can color the subset position data. 
After this PR, an opacity dataset cannot be used for a subset position data, while a color dataset can color the subset position data.