色が重なったように見える錯覚

くっついて並ぶと自然に見える

中の色だけ抜き出すと

奇妙な感じがする

It's an optical illusion that makes it look like the colors are overlapping. When they're lined up together, it looks natural. When you isolate the colors inside, it looks strange.

中の色の正解は

ひとつではない

There is not just one correct answer for the color inside.