The sky color, types of stars and atmospheric presure

[kikinho]

I read this interesting page: http://www.livescience.com/forcesofnatu ... e_sky.html

I was thinking about planets which orbit K and M stars. Would the color still be blue in these planets? The Sun rays bends blue light more than red light. But what about in K and M types?

I was also thinking if Earth had an atmospheric pressure 5 or 10 times higher than now. If the atmospheric pressure was higher, shorter wavelengths would be more difficult to reach the surface, and lower wavelengths could reach more the surface. So if I create a planet with atmospheric pressure 5 times than Earth orbiting a K star would the sky color still be blue or would have another color ( green or yellow, for example)?

[PlutonianEmpire]

For earth orbiting K or M stars, I think the sky would still be blue, but might have an orangish or reddish tint to it.

For a thicker atmosphere, I think it'd be red, with purple or violet sunsets. Remember, as the sun sets on earth, light rays have to travel through twice as much atmosphere, so the light refraction optical stuff makes sunsets appear orange or red.

[ajtribick]

Here's a thread you should probably read dealing with this issue.

[kikinho]

Now I'm creating a planet with an atmosphere of 60% nitrogen 30%methane 9%phosphine and 1% other gases. What would be the color of the sky on this world? Would it'll be green, blue or even yellow?

I think it would be bluish-green because of the high content of methane, but also have phosphine, which is yellow ( I think ). Maybe the lower sky would be yellow and the high sky be blue. But I don't know what would be the true color of this kind of air, so the reason I'm posting here.

About this planet:

The planet is made mostly of silicon carbide with many carbon rich minerals and also have a big content of many kinds of metals in it's surface, with a big ocean of liquid ammonia mixed with metals ( salts ), some sulphur, few chlorine and many organics. The core of this planet is mostly iron/nickel and have few carbon/sulphur.

So the two main questions are: What would be the color of the sky and the color of surface?