Spheres that change color, move across the sky and sometimes disappear.

Since January, we have been seeing these and recently they have been increasing in the numbers and nights that they are seen. They can start bright and then dim...or they can disappear altogether. They are small and round and vary from yellow, white, red, and blue...they move across the sky and veer, never staying on a straight course. It varies in speed and height. They make no sound and they will slowly disappear into the sky. There can be multiple lights and multiple times that they will be seen. We don't think that they are satellites and they are not planes.