Doflamingo definitely has blue eyes and bright blue ones at that. In anime the seriously insane demonic children have blonde hair and blue eyes.
Some examples are:
Alois Trancy
Shou tucker
Ryo Asuka
Luck Volta (he's a good guy but he's still got some serious issues)
Yoshikage Kira
Also, I headcanon that he regularly goes around forcing married women into affairs with him. Because we all know what tan skin and blonde hair means in hentai and considering the insanity of the one piece world, I'm applying it there too.
