rec 709's defines 6 colors its primaries.(7 if you count the white point as color)
If you quantize each component Y (luma) Cb (blue difference) Cr (red difference) at 10 bits you'll get 2^30 colors within the color space which is defined by the 6 primaries.
You are probably having problems with your video level and seeing these macroblocks is not because of the 10 bit projector.