Before they G4's were released they started making G3's with the Opaque cases. I wanted to do a similar thing were I had a transparent case from an older G3 that I was hoping to paint and then put onto my newer iBook G3. I found out that the transparent casing had a cushion lining type thing on the inside of the bezel. When I went to try and fit the transparent case on the newer G3, the bezel did not fit because of this cushioning. Like War said, it may be a little work to get it off but I think the colored look is definitely worth the effort.

After writing that I went to take a picture and realized that it's more of a glue material on the inside of the bezel (which I am pretty sure can be easily removed). It was a combination of this and that the inside of the newer iBook was larger so there was an obvious gap around the sides. But hey, I say go for it!