Hello,
Yes, your code is correct, that's why I investigate directly in your backend to process somes tests.
To better understand my answer, you have to look my previous documentation link, in your backend, I create a custom version of the default frontend css file, and your css command (posted in this
here
) are at the end of this custom frontend css file.
And so, now your button shown in your second screenshot are blue, and you can proceed like me to going more far in your adjustement and customisations.
Hope this will be more clear, and will show you how to proceed.
Regards