I'm looking for 5 png images, each containing a separate colored bubble graphic. Each bubble should be at least 50x50 though it should scale down beautifully to 25x25. The initial usage will require the smaller size. These will be used to replace the set as seen here:
Each bubble graphic must be contained on a transparent background such that the resulting png image can be seamlessly drawn and moved over a background containing any pattern.
Bubbles that resemble Mac OS X titlebar buttons or bubbles that would nicely fit in with an Apple operating system will likely be heavily favored. If each bubble could also have some distinguishing factor for color blind people, that would be incredible.
Another reference design could be the old Puzzle Bobble / Bust-A-Move game as seen on wikipedia:
Outstanding color, beautiful touchable bubbles, and internal designs differentiating by more than color.