Astronomy: Why do Mars and the other planets seem as stars in the sky, having different colors, such as red?

Even the nearest star after Sun appears as a point disc with an ordinary telescope. So, light from far stars go through thick atmosphere of the Earth (refraction!) and appears as what we call as twinkling. However, light coming from a planet does not seem to twinkle. The thumb rule is that the closer the celestial body to us, the lesser it will appear to scintillate. It happens because they appear bigger than stars and light from edges of the planet cancel this kind of random refraction through the atmosphere.

Due to increasing city lights and pollution, the planets are appearing fainter and fainter. The pollution layer is juxtaposed over the space view and reduces the actual color information. This is like putting a translucent rice paper above a red apple. You will see it lesser red. That is why it is really difficult to point out the color of the celestial body. I believe you can see Mars and other planets in near true color when seen from places away from city lights and pollution.

An interesting fact worth mentioning about Mars is that, it sometimes goes further from Sun than Earth from Sun. This causes it to appear brighter or dimmer (based on proximity to Sun). When dimmer and low in the horizon, it might also appear to scintillate.