Say, has Himura Kiseki ever done a color picture of Ai-chan (aside from this one)?
I mean, she's commonly depicted with blue-ish eyes in fanart. And the anime also gave her blue eyes. But she has brown eyes here.
Not that I mind either way. She's cute regardless of Ai colors.
Why yes, yes he did. There's post #2667432 where she does have what appear to be blue eyes, and there's the cover pages for the various official manga, which while blue-tinted do show non-blue shades such as brown hair, so the fact that Ai-chan's eyes remain decidedly blue-colored strongly implies that's their actual color.
Perhaps the brown shade we're seeing here is either an error or a visual illusion caused by her squinting (she has rather long eyelashes, no?).