Hello @Ellen99,
Do you mean the colours on available days or on days with a reservation request?
Reservations will show in green if they are confirmed. They will show in orange/gold if they are pending acceptance by you or while Airbnb waits for the guest's payment to be confirmed.
A green colour on an available day means that the price set is below the Airbnb price tip that would apply if you accpeted their price tips. A gold colour here means that the price is slightly above the tip. A red colour means that the price is significantly above the tip.
You can view the price tip for any available date by clicking on it. The window on the right will show the selectable price tip and a breakdown of the calculation behind it.
Steve.