Three things to think about:
1. Does it work with the palette loader of whatever program / platform you want to use this on? I can imagine that the extra colors might be a strain on a SNES engine if not done right, for example. Though if it's for a PC project, I don't think it'll be that big of a problem.
2. I personally don't think the sheen of white pixels in row 2 is the best way to go about it, unless you're trying to give off the idea that the cape is reflective, or is made out of, say, waterproof materials like polished leather or polished rubber. Otherwise, I recommend the solid red, unless you can find a tone of red halfway between that base color and white. (Point 1 applies, of course.)
3. I'm guessing you want to include some sort of billowing animation for when the character is walking, right? If you want to add some livelihood to the sprite sheet, you could include some extra frames when the character has stopped walking, for the cape to float gently to a standing, idle position. Maybe 1 or 2 maximum for this sprite size and color depth. Think like how the Super Mario World Cape Mario cape sprites float as Mario walks and jumps, and take a few moments to "cool down" after the character stops moving. Just something to think about!