Make dark mode buttons fit for dark mode

[tijlleenders]

Is your feature request related to a problem? Please describe.
It's very annoying when you're in dark mode and the buttoms are not compatible / readable.

Describe the solution you'd like
Find a better design.
Validate that with team.
Implement it.

Describe alternatives you've considered
None.

Additional context

[vinaybadgujar102]

@tijlleenders, we can opt for a darker version of the color.

[tijlleenders]

Is that just a one-line change?

Please use a contrast checker to see if it conforms to accessibility guidelines.

[vinaybadgujar102]

Is that just a one-line change?

Yeah it will be one line change.

What about other themes?

[tijlleenders]

Cool, we can do that then. It looks good.

Just make sure the contrast levels of all themes are conform accessibility standards.