Green screen

I've been told I need a new "Picture tube" for my Sony KDP65XBR2 rear
projection HDTV, however it was recommended that I replace all three RGB tubes for accurate color balance, this suggestion from the authorized Sony repair center (TOPS) electronics. I contacted the MFG of the Tubes, who tell me that I DO NOT need all three to get an accurate representation of color), the repair center tells me that the Blue tube is not longer available (HDTV is 6 Years old) I paid $6000.00 for it, a thousand a year sounds a little iffy. The manufacturer of the tubes (for most projection TV's) Says they are all available for $152.00 each. Is it worth repairing, and if so do you recommend buying spare tubes before they are really discontinued??