Sorry, Byrd, but CRTs operate under such high vacua that no contamination by moisture occurs. You have no idea just how close to perfection the vacuum must be for a CRT to work at all. A leak sufficient to induce moisture-related damage to phosphors would cause much more dramatic artifacts.

If you see mottling/rainbows/etc. on a color CRT, suspect a degaussing issue, or a mechanically damaged shadow mask. But a leak? No way.