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):

[Linked Image from tlc-direct.co.uk]

Most others are just plain black handles for all ratings though.

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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:

[Linked Image from tlc-direct.co.uk]