before you can get any help you need to be specific about what you have.
red+blue+green = component video (+red+white audio)
yellow = composite video (+red+white audio)
to go from hdmi to either of these you would need an active adapter box. older tv units sometims have svideo, which would be another option available with an active adapter box if your tv supports it.
now it should work, but i can not guarantee it because it may output a resolution that is not compatible so you might get odd display on screen or possibly no video if instead of stretching the image your tv just ignores non supported content.