Use variable styles and it automatically changes depending on the theme applied by the userCan be, but won't be. Whilst technically possible to do, it can only be done by site admins.
It requires a bit of theme customisation on the back end, and you have to then edit multiple themes on Xenforo.
Also means every update you have to ensure the themes don't revert back.
For example if you made them bolder and a darker blue, then on a light theme they'd stand out, but they'd be hidden in text for people using the dark theme.
Hence for a small change it can actually be far more trouble than the problem it's trying to resolve.
I must say it's been quite some time since I've looked at the Xenforo styles area, so didn't realise that was possible.Use variable styles and it automatically changes depending on the theme applied by the user.