Hey @jules03 
Let me see if I can get some answers for you!
I’m not sure about what color September would be, as I don’t usually give colors to months. As far as planet and sign goes, the months aren’t split up that way. This is actually the sign itself.
There are two signs for September. The first is Virgo (August 22nd to September 22nd), and Virgo is ruled by Mercury. The second sign of September is Libra (September 23rd to October 23rd) - ruled by Venus.
I hope this helps! Please let me know if you have any other questions.
We also have an entire collection of astrology posts here → Astrology Information 🌌