Is the blue tube projecting a sharp picture? Or are you seeing
bleedover caused by dirty cooling fluid?

I heard somewhere that the blue tube typically runs hotter, and the
cooling fluid clouds up and eventually degrades the image. Replacing
the fluid is not trivial but a lot easier and cheaper than replacing
and aligning the tubes.

I don't know why it would go away after warming up, unless whatever is
obscuring the picture goes back into solution when it's warm.

Mr. Land wrote:
However, I have noticed one problem with the pictu after the set has
first been turned on and for a few minutes afterwards, if there happens
to be a bright-to-dark vertical boundary in the picture with white to
its left and black to its right, there will be an uneven, splotch of
bright blue color all along the right side of that boundary, looking
almost like a bright blue, sloppily-painted thick vertical band of
color.