Giorno’s got blue eyes in the digital color manga that came out a few years ago (the color choices were handled by the company who did the colorizing rather than Araki himself).
In Araki’s own original color artwork though, Giorno having gold eyes is standard:
It’s jojo so there’s alts (and most of those match his eyes to his hair: blue eyes with blue hair, purple eyes with purple hair, etc). So purple, green, blue and even pink all join the list … as alts.
But as for what’s considered “standard,” it’s Gold (or a warm, golden-type tone). fwiw his figures almost always have gold eyes too:
You cannot ground DIO 