Coloured text against coloured background
How to use it
When placing text on a coloured background, colour the text as well. Either a light tint for dark backgrounds, or a dark shade for light backgrounds.
When to use it
Pure black text against a coloured background can look flat, or unnatural. If you add some colour to the text, it'll feel like it fits in more, and suit your branding more on top. Using shades and tints of the same colour keeps the interface as monotone, and means that it stays simple.
What to watch out for
If there's no enough contrast between the foreground and background colours, you'll run into accessibility/contrast issues. This technique works best if the dark colour is almost-black, and the light colour is almost-white.