Sound but no picture or picture & no ...

DVD player works great but on vcr side, we get either sound & no picture or picture with no sound.  When we get sound & no picture, we get a blue screen with butterflies on it.  There is no place to plug in the yellow video cable on the back of the tv; but the vcr comes on when the dvd cable is plugged in the dvd spot and we hear the sound but there isn't any picture.  Are we doing something wrong, is the cable bad or is the tv not compatible with the dvd/vcr player?  Thank you for any information.