DAZZLE is to confuse their eyes as last time they dont have accurate computer aided targeting system, but nowadays every single warship has been fitted with at least 1 SSM with guidance or heat seeking

as grey is their best bet as they didnt stand out like DAZZLE with multiple colours, due to vapourization, the sea is almost misty so if painted in grey, it would result in a very invisble like effect, DAZZLE will be spotted as soon the ship is in their range of sight