SCEPTRE X322BV, HDTV BLUE LED COMES ON WHEN POWERING UP, BUT NO PICTURE OR SOUND

I can't find a manual for either of these sets so I'm not able to be specific with parts but a set with no sound or picture is generally caused by either a bad main board or power supply. You can find out what board is bad by checking the PSON..stands for power switch on , the voltage should change when you push the on button and stay that way but going by the fact you get a blue light I'm guessing that is working and you have a bad power supply, another test would be with the set on and the light blue test the various power supply voltages and see if any are missing or incorrect, the values should be on the legends next to the connectors, they will say for example pin 1 ground pin 2...12 volts...pin 3... ground...pin 4.5 6...5 volts ect....Good luck!!

A blue screen usually indicates no video signal.

Check in menu to see if the region is set to Pal Europe instead of NTSC.this should restore colour.if it is already set to pal and giving black and white then switch it to NTSC

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/

Fault with its main board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. http://electronicshelponline.blogspot.com/ . In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

Check the speaker/s first. If found OK; check and replace the damaged component/s at its audio output section circuit board. If needy, replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. Surf the site with patience.
http://electronicshelponline.blogspot.com/

Sounds like The main power supply regulator section circuit fault. Either it will be a separate board, or the part of main board. Check and replace damaged component/s at its main power regulator [SMPS] section circuit. Contact any service technician. If you wish to get some details; check the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/
It will be best to replace the power supply regulator board as card basis rather than making "Surgery" to it; which usually will make loss for both money and time. Even though you can make it right, it will cost around an amount equal to the cost of a new board; including the cost of (spare parts + service charge) More to say, most of the spare parts to it will be difficult to get from open electronic spare part market. This is true to most of the flat panel TV power supply boards; irrespective of its brand and screen size.

do you have sound?

if that is brand new and still covers on warranty you need to do is get back to the dealer for repair or possibly replace