1. You can use the same code from your other topic, I just replied to you there.
2. Do you mean these buttons? https://www.screencast.com/t/QAr2IDVJghg
If so, they seem added by a plugin, the style is defined by the plugin, unfortunately, GP has no control over it.
As for the colors, try modifying the colors in Appearance > Colors > Buttons. Try checking the Block settings of the Button Blocks if you’ve set a color there as well.
And regarding the button, as they’re not GP ones it’s not controlled there. Its something to do with the link colour, but why is it being overridden in a button?