maybe follow the manual...
quote "TV may require service.
Hold power button on front panel for 10 seconds to reset TV.
If LED continues to flash red and yellow after reset, turn off the TV and
unplug it from the AC power source. Wait one minute and then plug the set back in.
If LED continues to flash red and
yellow, go to www.mitsubishi-tv.com or call 1-800-332-2119 to receive Authorized Service Center informa-
tion. You may be asked to count how many times the LED flashes each color to aid in troubleshooting."
Lastly, ensure that all the cabling has been checked going to the light engine... perhaps you disconnected a cable "accidently". Still further, does your color wheel attempt to spin up?
Probably the first question should have been "why did you change the lamp?".