you want a 6' fixture. they do make them. they are 6 or 8 x 39 watts per side. i would definitely go with 8 lamps per side. i knew a guy with a 30" deep tank that had a 14 lamp (7 per side) fixture and he kept clams on the sand bed, so 2 less lamps isn't going to kill you, but if you can pick up a fixture with the extra 2 bulbs easily, i say go for it.
if you do have a decent canopy you can screw lighting to, i would use the 60" lamps and stagger them. as far as the colors, there are a few different options per each bulb company.
let me know what you end up with and then we'll go from there.