Buttons
Variants
Background and foreground variant
Often, you might want to have a button that follows the background/foreground color. The easiest way would be to use the background/foreground variant. When on light color scheme, background will automatically refer to the light color variant and foreground to the dark color variant. Same goes for the dark color scheme.
CTA Button
CTA (call-to-action) buttons usually need a bit more of a oomph to get users more likely to click on them. This is usually achieved by making the button more eye-catching.