Your design is nice and simple and looks good on all the options. I like #4 best though and think that the blue on black will look great. I did the reverse - black on blue for my $1 chip and it looks great. Here's a pic of the finished product.
#4 looks great. Everything looks great actually! Go for it!
The only thing I'd do is increase the size of the denom a little bit. It looks fine on screen, but might be a bit small when printed. Try printing it at the real size it will be to see how it will look in real life.
I ran into the same problem when designing mine. Printing is really an eye opener to how the finished product will look.