Why do most box legendaries always have the Red vs Blue color motif? Like every box legendary has blue OR red (or a shade of them) as their main color. With the exception of black and white, but they had some of that color in BW2
Blue:
Lugia
Kyogre
Dialga
Lunalaa
That blue dog

Red:
Ho-oh
Groudon
Palkia (red shade)
Solgaleo
That red dog