In #3250 we are adding support for custom plotly themes and in #1698 we want to support dark mode.

For these to work nicely, MultiQC shouldn't assume white backgrounds and hardcode hexes that are appropriate for that. Instead, colours should be highly saturated but with very low opacity. When done right, the resulting colour on a white background is identical, but it adapts properly to differently coloured backgrounds.

I've manually switched out some colours for background bars in #3250 but this also needs doing elsewhere:

• Colour code that generates hex codes for table value bars
  • Lighten colours with alpha instead of admixing white #3252
• Checking more plots to switch manually
• ..probably more places once we start working on dark mode properly.