Back when I ran halides on my gig tank, I used 6,500k Iwasaki bulbs with actinic VHO supplement (wow, I'm really dating myself). My gigs loved white light. Nowadays I have my gigs in two tanks: two gigs under both Radion G5 Blues running the AB+ setting so the tank is really blue (my green gig glows and the purple one pops) and the other two gigs under Kessil A360xs running a more white light (my blue gig actually looks a bit drab under it and the tan one looks.. um... tan). The two magnifica in the tank love the bright light, too.
I'm starting to suspect that the blue and purple gigs may come from lower depths compared to the tan and green ones. It may also explain why the tan ones are the most common, followed by the green ones (though obviously it could just be distribution and collection sites). In other words, those two may prefer a whiter light, while the other colors prefer a bluer light. Granted, this is all just anecdotal and based on my observations of two tanks.