[QUOTE=Mangetout]
Yellow, with yellow dots of a different shade.
[/QUOTE]
This past weekend, I saw a suit that made me think of the song - it was indeed yellow with paler yellow dots.
Why don’t they update this…it is so 1960’s…how about 'yellow polkadot thing bikini"?? 
[QUOTE=phouka]
Huh. Never questioned this before. I see it as yellow background, black dots.
Also, for some reason, that song is inextricably linked with One Eyed, One Horned, Giant Purple People Eater in my brain.
[/QUOTE]
Purple people?!
Same here.
Since the song causes blood to shoot out of my ears, I’m always too distracted to think about how the bikini looks.
You should see a doctor about that.
Black, with yellow dots. Because it looks hottest that way.
Yellow with large dark-brown dots.
I doubt that the singer cared how you pictured the outfit–you were supposed to picture her without ever seeing the bikini.
As I recall, bikinis used more material back then. Nowadays there isn’t room for more than one polkadot on a proper bikini. 
Not that that’s a bad thing.