Tiny but frustrating bug in Supraland Six Inches Under (spoilers!)

In the final area, the green guy wants an apple. I already gave him a green one and he was saying that maybe it was the color. Apples are commonly red so I went to the bank and painted the green ball with red paint. I did the long journey and brought it to that guy. He said "its still green!". I didnt understrood that. I was very confused when I found out that you need to give him a blue one.