Hi Allposition,
A GameCube can display black and white when the video cables aren't hooked up correctly. Most GameCube cable harnesses have [https://en.wikipedia.org/wiki/Composite_video|composite|new_window=true] cables, [https://en.wikipedia.org/wiki/Component_video|component|new_window=true] cables, or some combination of the two. If you inadvertantly mix up these connections, the video will display incorrectly. I'd check the back of your TV to make sure your system is wired up correctly. If your setup is correct, you might actually have a faulty cable harness. You can buy replacement cables [http://www.amazon.com/s/ref=sr_st_relevancerank?keywords=video+cables&fst=as%3Aoff&rh=n%3A468642%2Cn%3A294940%2Cn%3A541022%2Cn%3A353832011%2Ck%3Avideo+cables%2Cp_85%3A2470955011%2Cp_n_is-min-purchase-required%3A5016683011&qid=1458007842&sort=relevancerank|here|new_window=true].