Bad DVD picture

I had a Memorex DVD player that displayed a fine picture on my TV, but unfortunately, it went dead. I bought a new Magnavox DVD player at WalMart and the picture looks washed/whited out in parts, almost as if a bright white light is shining on it washing out some colors. I returned the player and replaced with Sony with the same results. I returned that and tried a Philips player with the same result. I am hooking the player to the TV via an RF modulator since the TV is 19 years old. I am connecting using the cord with White to Left, Red to right, and Yellow plug to Video In/Out. My TV colors look fine with the VCR and with broadcast TV signal. What can be the problem?