How do I mute a colour, or make it less saturated?

Muting a colour means reducing its saturation, moving it toward grey while broadly keeping its hue and lightness. This can be done directly (reducing saturation), or by mixing in a touch of its complementary colour, which neutralises some of the original hue's intensity — a classical paint-mixing technique. Optical mixing (small dots or fibres of two colours viewed from a distance, as in some textiles and pointillist painting) can also read as a softer blended colour without physically mixing pigment.