Color + Mix should only happen after the piece is locked and R&C has signed off with all hi-rez and vetted archival in the cut. Blurs can happen after color is laid in.
PLEASE give advance notice as it takes time to grade every frame and mix all tracks for the piece. Good timing to request color and sound is when your fine cut is first sent out for notes
Have a budget: colorists and sound mixers are freelance
Pro Tip: If your piece is 20+ minutes in length, schedule at least 2 days for color + mix + review. List these days in your project calendars.