Husband dx with cellulitis on his foot. on antibiotics for over 24 hours. swelling and pain have decreased, but redness & bruising increased. normal?

Yes, pretty normal: Cellulitis doesn't respond to antibotics overnight; it takes a few days. The reduced swelling and pain are good news, so no serious wories that redness has increased. Contact the doctor treating your husband if it actually gets worse (more pain, more swelling, higher fever) in the next day or two; or if no significant improvement after 4-5 days. Or call any time if still in doubt.