Change code highlight color when double-clicking on a word

Hi, I'm a longtime R&Notepad++ user switching to Mac and RStudio. I have the same problem as in this previous discussion (and frankly very surprised this is not an option setting considering other code editors highlight selected words in much more obvious colors)

In short, I followed the suggestion to https://tmtheme-editor.glitch.me/ and downloaded and activated a theme (Notepad++), but the code highlight color remains unchanged. In the online theme editor, I also don't see any option to customize the highlight color of a selected word either.

Let me know if you know a solution; I'm finding it very hard to get used to this 'quirk'.

Thank you so much!!

With how popular (hyped?) RStudio seems to be, I am a bit surprised by the lack of Posit support. I've been wanting to buy and run an RStudio server soon but less sure now. Perhaps there's a more active support community elsewhere for basic program functionality? Thanks for any tips!