Ah! It's a prejudice.

[Ryou grins a little, before deciding to fill him in.]

See, people associate 'pink' with 'girl', these days. I don't think it's all that old a tradition, but it's pretty common now. 'Bright and pink' usually means 'girl'. While 'somber and blue' means 'boy'. So people get really riled up about pink being girlish.