Okay, now that you've said "not enough blue" instead of "no luck getting close to a blue color", I think most people will refer you back to adjusting all three pots. It'd help if you had a way to load the 240p test suite on your console because then you could open the handy test pattern that shows red, green, blue, and white color bars. It'd give you a better idea of what's going on.
Also: both my LCD and my CRT have a way to display only red, green, or blue signal alone. See if yours does, and take a look - it could give you a better idea of the problem.