I have some research I want to do about a planet for a novel I'm writing. It is a fiction/science fiction novel, but I do wish to actually have some parts of the world correct in the scenes I depict.
So, basically this planet is situated in an entirely different solar system, with a similar star to Sol, but much more standard galaxy-wise. i.e. a Star roughly the same size, but component-wise, and light-wise, it is as average as can be.
The planet has about 4 times the surface area of Earth but is not tidally locked. It has its own perfect spot where it is able to rotate around its sun in about 320 days, and 'around itself' in about 20 hours - yes I know that is quite fast.
The Solar System has about 4 planets the size of Jupiter, and with this particular planet, there are only 2 other planets, each very small in comparison. You can think of them in any order, but they are at least partially visible as stars with the naked eye.
The moon orbiting this planet is about twice the size of our Moon, and is habitable, but yet uncolonized by the dominant species. Only normal life exists there, thus no external light sources on this moon. It is far enough away from the planet to regarded as equivalent in size to our Moon.
The plants on this planet should, theoretically, be able to operate at about 60% efficiency but are much rather red, and blue in colour with green scarcely found, but still found in the older species of the planet.
I figured to add this point since, from what I know, even if this might be wrong, larger planets have higher chances of being tidally locked depending on how close they are to the Star in question. Thus it should be pretty far out to not be tidally locked, but at such a distance where light is not exactly the same quality as on Earth, forcing the plants to be much more efficient.
The temperatures should also then be colder, but I figured with high enough amounts of greenhouse gasses it should be possible to at least make it somewhat livable. Specifically, I am talking about the more effective greenhouse gasses - whatever they may be at this point (I will do more research on this at a later point. The answers here should probably change the atmospheric constituents somewhat)
The atmosphere make-up is around 80% nitrogen, 8% hydrogen, 2% other gasses, and 10% oxygen.
So, I have a question about what one would experience on this planet close to the sea.
Would it be safe to assume that the sky would be a similar colour as found on Earth during sunset, sunrise, noon, and night around sea level?
Thank you for any and all help provided.
Edited: Removed unnecessary questions to follow the one-post-one-question rule. Explained Certain points in more detail.