Diagnosis
These are stuck pixels on the DLP chip (DMD). They are not dead pixels but micromirrors stuck in one position. This is a hardware defect in the chip itself. Dust on the chip can also cause similar, but larger, spots.
How to Fix It
First, rule out signal source. Change the input source to the internal menu or a different device. If the specks remain in the exact same screen positions, it is the DMD. Run the 'Pixel Orbiting' feature. Go to Settings > Display > Advanced. Enable 'DPC' (Dynamic Pixel Control). This shifts the image slightly to unstick mirrors.
If That Didn't Work
Persistent stuck pixels indicate a DMD chip failure. The PX701-4K uses a 0.47" Texas Instruments DMD chip. There is no user repair. If under warranty, contact ViewSonic. The pattern (clustered or scattered) determines if it's a chip or contamination issue.
Heads Up
Do not confuse this with 'color break-up' or 'rainbow effect', which are moving flashes of color seen by some viewers due to the color wheel. Stuck pixels are static, pinpoint defects.