Interesting shots. Of the two the top one I feel is stronger. #2 first though - I can see what you were aiming for but the marbles behind don't add much to the bokeh. Perhaps they are too uniform in colour? Also the brighter purple one on the right near the back is a bit distracting. Could be toned down though.
#1 I think is better. I'd lose the third, partial marble in the background and just focus on those two. The purple tinge added to the clear glass marble is a nice effect and contrasts well. I'd be tempted to try cloning out the specular highlight on the purple marble too; though not mega distracting I'd want to see if it looked wrong without it.
How far away is your light source out of interest? Have you tried different flash setting (if it's flash)?
Also try yellow paper - yellow/purple are good contrasting colours and it might make the purple really zing.
Composition wise its fine. You've gone for a square crop too I see
A marble based shot was on my list this year... once I buy some marbles
I was going to try a long line of marbles receding into nothing, all different colours on white, so if you get there first I'll be interested to see the outcome
