Hi. The other night I turned my television (25" CRT) to the side so I could see it from the other room. When I turned it back, the picture suddenly had a blue cast over it, like the tint was set incorrectly. Now it fluctuates back & forth between a normal-looking picture and a mostly blue picture. Hitting the side of the TV will sometimes force it back to normal. Is the picture tube shot?

Thanks! :)

Sounds like an intermiddent connection, May be a plug in connector came loose.
If you are comfortable with TV repair, and understand chassis can be hot(live), and the high voltage line to tube, then I would remove back, stay insulated and with insulated tool,
Poke around, jiggle and try to determine bad connection, Could even be a cracked board,
Or solder connection, Magnifier will help. A mirror so you can see picture will be helpful, or a second set of eyes. Stay insulated and Safe, Good Luck
Intermittent parts are less common.