I am building a model of the corsair and am not sure what the proper color is . In some pics it looks dark blue to me then in some it looks black .Can someone suggest a color ? Thanks.

I'm pretty sure most of them were blue for Pacific camoflauge. See if you can turn up some screencaps from the old "Black Sheep Squadron" tv show - they had several nicely restored Corsairs.

Late war, they were Navy Blue overall.

Early war, they were white on the belly, "intermediate blue" on the sides, and "sea blue" on top.

See this aftermarket decal sheet from Aeromaster, for examples:
http://www.eaglestrikeproductions.com/cgi-bin/amddecals.pl?scale=48&setid=151&dbs=aeromaster&pgs=2&currpg=1&dclimg=ad48151

All these colors are available in the Testors ModelMaster paint line.

Yeah sounds like you're looking at the Overall Glossy Sea Blue FS15042 color. It's one of the few glossy colors that behaves like a dream out of the Testors Model Masters Spray can and of course thre are myriad brands that you can use to brush or airbrush the same color.

Generally speaking, on the three color scheme that preceded overall Glossy Sea Blue, the top surfaces were Non Specular Sea Blue (FS 35042) the sides were Intermdiate Blue (FS 35164) and the lower surfaces were white.

All of these colors weathered in strange ways so many variations exist on in-service machines.

Poke around on the web and you can find out more.