Its has been five days after my histofreeze, burn skin is getting small blisters, why is that? Will my scarring will stay red?

This is normal. Typically after freezing, the treated skin will blister or scab up within a few days. The swelling may be worse two or three days after treatment. The scab will come off in a week or two, leaving a pink scar. The pinkness takes another few weeks to fade, leaving either a pale area or hopefully no scar. If the redness seems extreme or the area becomes painful and swollen that can mean infection.
Should improve. This can be normal and is from the cryotherapy. They should crust over and over time the redness should improve. Occasionally there can be pigment alteration meaning it can be a little white but that often gets better too. Sun protection is essential especially while it is healing.