My uncircumsise penis has become more red in color lately, sometimes flaking on the skin and the head is very shining at times esp when masturbating.....I just had std hiv test all NEG except that a reason for the redness of color?

Balanitis? No STD is a likely cause, but it's good you were tested to be certain. Probably you have balanitis, the medical term for inflammation of the head of the penis, usually in uncircumcised men. Bacteria and yeast can do this, but many cases just need improved hygiene (retract foreskin and wash with soap and water 2-3x daily). Usually not serious. Discuss w/ your doctor or a dermatologist or urologist.