Do clear solar covers really heat better than blue/black ones?

I don't believe they work any better than the blue/black ones. The reason that solar collectors are dark color is to absorb the most amount of light. Black color is composed of the whole color spectrum. In chemistry, blackbody means it absorbs all light falling on it and does not emit/reflect it back out. Basically if you have two room one lighter color and one dark color, you will notice that the lighter color room will appear brighter since light is being reflected. In a darker color room, the most of the light is being absorbed so it will appear dimmer. You'll notice that solar calculators have the solar collector in dark color like black.