For themes like One or PaperColor, there are dark and light versions. For dark or light theme, I usually add my own customizations like bracket color, comment color... etc.
I tried to combine them so that everytime I set background=dark or light, with an if else statement. I tried the following but it doesn't work.
if (set background=dark)
""" my own code here
Please let me know how to go about this and thank you.