IF you have access to PhotoShop, try running your Corel Images through it.
PhotoShop has an NTSC colors filter that does an adequate job.
Your safest bet is to simply tone down your colors from Corel. It is set to
give most colors at full intensity out of the box. Try creating a palette with
the colors down to 75% power. (As in, instead of 255,0,0 for red, try 192,0,0)
Virtually every NTSC converter will generate an illegal color, and cause
bleeding and crawling with full yellow.