As ever there is an element of 'it depends' about it. On a high to low intercept over the sea the sea state itself has a big part to play as does the sunlight (the sun would 'highlight' a lighter colour - and might glint off fighter and target alike). I have clear memories of struggling to pick up GR4 over the sea - and having to get lower, sooner to try to find them - whereas usually they were a little too dark to hide and stood out a long way. Conversely I remember looking down over the bright blue Scottish water and seeing a F-3 as bold as if it were Dayglo. With an overcast and some surface spray the lighter grey of the F-3 would probably be quite effective. Of course, that's only the visual spectrum catered for.
Any leader worth his salt would spend a significant part of the plan getting to grips with the environmentals and where they would favour you vice the opposition. Naturally when you got out and about you'd occasionally find your thinking a little wide of the mark!