They colour Mars red because Mars is red. The following is a photo that I have taken through a very small telescope and you can see that the planet is red.
I have just seen your image of Mars; it is very nice indeed.
However, some planets like Venus appears blue; other planets like Saturn or Jupiter may appear yellow or orange; but this is only apparent to you from far distance; it is not due to that Mars is truly red because it has much iron, nor Venus is less than it in iron or that the other planets have copper or other materials in abundance; although all these elements are present there on all these planets; because all the planets have a common origin.
The reason for the apparent coloration of the planets is their position and distance from us and from the sun; whether the planet is before us (in relation to the sun); so that the sunrays fall on it (before reaching to us), then it will be reflected from that planet to reach us.
On the other hand the planet far from us, the sunrays will reach to it after passing us, then they will be reflected from that planet and we see that planet according to some light waves that are reflected giving the planet that blue, red, orange or yellow.
While the planets almost have similar constituents with some variation and modification, like that you see some regions in the Earth rich in iron, copper, calcium or other elements.
eanassir
http://universeandquran.741.com
However, some planets like Venus appears blue; other planets like Saturn or Jupiter may appear yellow or orange; but this is only apparent to you from far distance; it is not due to that Mars is truly red because it has much iron, nor Venus is less than it in iron or that the other planets have copper or other materials in abundance; although all these elements are present there on all these planets; because all the planets have a common origin.
The reason for the apparent coloration of the planets is their position and distance from us and from the sun; whether the planet is before us (in relation to the sun); so that the sunrays fall on it (before reaching to us), then it will be reflected from that planet to reach us.
On the other hand the planet far from us, the sunrays will reach to it after passing us, then they will be reflected from that planet and we see that planet according to some light waves that are reflected giving the planet that blue, red, orange or yellow.
While the planets almost have similar constituents with some variation and modification, like that you see some regions in the Earth rich in iron, copper, calcium or other elements.
eanassir
http://universeandquran.741.com