Recently, I started to use the Rsutido theme Summerfruit downloaded from online tmTheme editor. This theme specifies green background for R script comments.However, it conflicts with the background highlighting for text selection. Theoretically, text selection should overwrite the background color pre-defined by the theme. However, this does not happen and lead to great visual difficulties to identify selected text. Hopefully, this bug could be fixed soon.
If you are sure it is actually a bug, then the official rout is the Github repo (just make sure to follow their guide to do it), but if you are not sure, then it is better to start here and when you get confirmation then move on to the repo.