The male cardinal is bright red. the female is a dull brown. why are the two birds different colors?

The birds developed different things that were needed for their survival. The reason that the male cardinal is a bright red is because he needs the color to attract females for mating. The females don't have the same problem, so they didn't develop that gene.

Mars and earth have quite a few things in common. both are  terrestrial planets, both are located within the sun’s  habitable zone, both have  polar ice caps, similarly  tilted axes, and similar  variations in temperature. and according to some of the latest scientific data obtained by rovers and atmospheric probes, it is now known that mars once had a  dense atmosphere  and was covered with  warm, flowing water.