This is because we actually strip out all background colors from table elements when we go into dark mode.
Idea: instead of stripping the color, we can try modifying the "brightness" of the color to be darker, e.g. (r/2, g/2, b/2).
Here's a screenshot with RGB values halved (rather than stripped) for table element backgrounds.
The good news is that it looks fine in general; the bad news is, as is the case here, this can also change meaning; the colors in the key (which we've just restored) no longer match up to the seats in the diagram.
Checked with 2.0.108-alpha-2015-08-12 on Nexus5(Android 5.1)
Samsung Tablet Ce0168(Android 4.0.4)
The 'Quick facts' for the national assembly of Pakistan article are displayed as in the screenshot by @Mholloway.
Checked on other articles with the same Quick facts structue with colorbox(es)-National Assembly (South Korea), Scottish Parliament, National Assembly of Quebec(no colorbox ).