This set of doors has had water ingress for a few years and I was asked to see if a) we could solve where it was leaking and b) to paint it white to match the other doors and windows which are a white PVC style.
FIrst I removed as much of the old frame sealant from the outside and the edges, this showed me that the sealant had not been working as most of it was loose and fell out, what remained was rock hard and cracked.
Then I sanded back the wooden trims and door sill and repainted it gloss white, the following day I re-sealed with a new white exterior frame sealant that I trust to last and incorporated some white PVC edging strips to prolong the sealants life and to hide the marks left from the old brown mastic.