Friction Blisters: The presence of multiple blisters on the top of the foot, a common area for friction, especially if the patient has been wearing new or tight shoes, makes this the most likely diagnosis. The slight redness could be due to the friction and pressure causing the blisters.

Contact Dermatitis: This could be due to an allergic reaction or irritant causing the blisters and redness. Common culprits include certain materials in shoes, socks, or topical agents applied to the foot.
Eczema (Atopic Dermatitis): If the patient has a history of eczema, the blisters and redness could be part of an eczematous flare on the foot.
Insect Bites: Multiple bites from insects like mosquitoes or bed bugs could cause blister-like lesions and redness.

Cellulitis: Although less likely given the description of blisters without significant swelling or fever, cellulitis is a serious infection that requires prompt antibiotic treatment. The redness could be an early sign.
Herpes Zoster (Shingles): Uncommon in this presentation but possible, especially if the patient is immunocompromised. The blisters could be part of a shingles rash, which would require antiviral treatment.

Bullous Pemphigoid: An autoimmune disease that can cause blistering skin lesions. It's less common and usually affects older adults.
Pompholyx (Dyshidrotic Eczema): Characterized by small blisters on the hands or feet, often associated with stress or allergies. It's less likely given the location and number of blisters but could be considered if other diagnoses are ruled out.
Epidermolysis Bullosa: A group of genetic conditions that result in blistering of the skin. Given the acute presentation and lack of history, this is very unlikely but mentioned for completeness.