I am aware that standard BS88 fuse holders are available in 4 different colours (Black, White, Green & Grey). In principle I've only ever used the black (fusing for power & control circuits up to 400Vac) and white (neutral links) but have never come across the Green or Grey?

Can anyone offer an exact definition for what each of these fuse holder colours types are, indicating what application they are to be used?

Thanks

Apparently they were used in the power generating industry to signify different circuits. GE have now stopped manufacturing these (Grey and Green types).

There is or was an ESI standard which is as follows
white = link
green = 16A
grey = 10A
black = 6A
blue = 4A
Violet = 2A
The blue and violet ones are usually painted. The colour only signifies the rating not the circuit function. The purpose of the colouring is so that fuse carriers do not get put in the wrong base, assuming they are correctly loaded of course.