Totally agree with Craig, I'd got for the magical production of the first ball with the purse frame. I'm not 100% sure about the colour change but if you are going to use it, now is a good time. One way I do the colour change is pop the ball in my hand and ask the spec to name a colour. If they say red then your laughing. But even if they say another colour it doesn't matter, say 'ummm no, another colour' and if you still don't get red say something along the lines of 'no no no, you're meant to say red'. That can be quite good, a nice little bit of comedy coupled with a nice colour change.
And why not magically produce the second ball, pull the one ball into two or perhaps saw it with your finger. Oh have you ever noticed that if you give a sponge ball to a spec to hold and have them sing to it, it somehow splits into 2?
I'm not a huge fan of the 10 count, just doens't seem to make much sense to me, but perhaps it does fit in your routine.
2 in the hand one in the pocket is always a nice way to finish a routine.
As for patter, I've recently pinched the idea of Spongeballs as Martians from the toolbox. Opens up a few fun possibilities when it comes to patter.
Good luck with it
