The Wylex plug-in breakers here (which can be used to replace rewireable or cartridge fuses on the older "Standard" range of Wylex panels) use color-coded handles (colors as listed above, plus green for 40A):
Most others are just plain black handles for all ratings though.
I've always gone along with the idea that the Main Switch on or in a switch-board should have a red toggle on it and no other colour.
You'd like the Wylex NH, GE panels, and a few others current here then. This is the NH: