Color can be either sex, but they have feathers, not fur.
Yup.
That means they want attention and their not necessarily mating they are interacting with each other. - Marisa Hope I helped:D
Is the color of the cere closer to a blue or a pink? A cere can change depending on the age of the parakeet only time will tell but if it looks blue it is a boy and if its pink its a girl!!
By colours you mean mutations. Budgies come in many different mutations. This is a good guide to mutations: http://www.budgieplace.com/colors.html