Is it normal to be this red after hair transplantation almost 4-weeks post-op? (Photo)

Redness should subside usually after one to two weeks.  However everyone heals differently and redness can also be a sign of infection.  If you are concerned you need to see a doctor for a recheck.  FYI your photo does not show any redness (it's just a very small rectangle of unfocused blob)

In general redness usually fades in 3-5 weeks. Those individuals with lighter skin complexions may notice the redness persists a little longer. Rarely redness can stay several months until new hairs come through to cover it altogether. 

persistent redness occurs in people with histamine sensitive skin but eventually it will go away, so be patient. Make sure there is no infection present