What would cause my picture fade red and then go back 2 clear picture,i have i have a 51 projection tv model#51f59,bought it in 2007.

Howdy...Your set is not completely familiar to me but the technology is . It is very odd for both Blue and Green guns to drop out momentarily . You would need more observation of tubes . I would get the front screen off and see if I can spot the tubes going dark or dim . It may not happen often . I would also get the back off and scope out all surfaces for evidence of leaking coolant . The expansion bellows may not be easy to look at behind shielding etc. but they will show cracks better . I have seen this occur in sets that were left on a music channel from satellite receiver blue screen for instance . These sets were not designed to have one solid color for long periods . this coolant can corrode all kinds of circuits . The refill can be got at a lot of electronic wholesalers , the rubber can be repaired but probably best with manufactured part .
There could be an issue with aging capacitors , these can be visually spotted sometimes with swollen tops/leaking . Best with an ESR meter though .
Good luck
Hugh