To answer your last question first, I would say the yellow is equivilant impedance of the red and white of that set.
But I would match the ctr and rears with the same cable you use on the fronts, if at all possible. If not at the very least try to match the fronts and center. You want to maintain the same timbre and voicing across the front. This advice is based upon the assumption that your speakers are of one model line, your amplification is either a multi channel or you are matching brand or model for all channels. And also if you are matching speaker cable as well.
But I would match the ctr and rears with the same cable you use on the fronts, if at all possible. If not at the very least try to match the fronts and center. You want to maintain the same timbre and voicing across the front. This advice is based upon the assumption that your speakers are of one model line, your amplification is either a multi channel or you are matching brand or model for all channels. And also if you are matching speaker cable as well.