I have a lg 37lb1da tv that is flashing red blue green when you turn it on

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. Viewing it in "Mosaic" or "Magazine" will make surf easy.
http://electronicshelponline.blogspot.com/
Blinking codes details to many popular brand TVs are given. Surf the site with patience. Do a search by type in the brand name of the device to the search box.

If your using composite video with the red green and blue, make sure the green and blue wires are connected to your TV right and not reversed.

most likely the inverter board is faulty, I think this model has two of them, look on ebay for cheap replacement.

Bad Capacitors in the Power Supply Take to a Good Technician

Hello,

Power supply board just die.It can be dead at anytime.Tries websites Shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.

Sounds like it's in a service burn-in mode. LGs need a service remote to de-activate. Probably easy for a local LG shop.

Power supply board is dead,replaced the power supply board will get power.

I have seen problems similar to yours in the past. Several causes can make the channels change by themselves. Some corrosion on the main board near the channel up/down switches for one. The next common cause is that the EPROM may be failing or a fault with the main control processor. A good test to see if the EPROM is having a problem is to program in all the channels off the cable and then unplug the TV over night and then plug back in the see if any channels are missing.

Your picture tubes are trying to short out you have 3 red, green ,blue.