Help xbox 360 problems need hlp?

hi ok i brought a 52 inch lcd tv 2 days ago and wanted to see if hd would work on the xbox 360 so i read what colour av cable i had to put in to i put the green cable to the green socket then blue then red and so on but when i put my xbox on it didnt work so then i changed the green cable and the blue cable and swaped them then my xbox start to work think that worries me is wasnt the green supposed to go in the green hole and the blue goes in the blue hole can anyone hlp me for using my xbox on hd and can you tell me what to do