How to disable syntax highlighting?

[oriyia]

How do I disable syntax highlighting and use my own theme? I found how to redefine groups, but I don't want to just disable it.

[ixru]

I don't understand what you're asking. The syntax just defines how your theme is applied. If you want to apply your own syntax I don't know the correct solution, but I think it might be possible by just placing the syntax file in the runtimepath. Whether before or after the plugin loads I don't know.