I bought a sense 42" lcd hdtv and the first time i hooked up my xbox 360 I connected the hd wires and set it to hdtv! It worked first time, now when I try it the colours on the screen are wierd red comes up as green and I don't get any

I think you're just hooking the wires up wrong. If, at first you don't succeed... try, try again.

try unpluging all wires from your hd including any cable/dish inputs as well as dvd & 360 cords. unplug your tv for five minutes and wipe off all male parts from your component/hdmi/dvi/av wires and wipe the outer female inputs on your hd & blow on all after wiping. hook everything back up and cross your fingers! also make sure that your 360 is set to hdtv(the external switch on the back of the component wire in the back of the 360) good luck!