ΔE 21.5, loose: different enough that you should pick on purpose. Titan Buff is noticeably lighter, much more muted than Plaguebearer Flesh. They are different kinds of paint: Citadel Plaguebearer Flesh is a one-coat contrast-style paint and Golden Titan Buff is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Titan Buff is noticeably lighter, much more muted than Plaguebearer Flesh. They are different kinds of paint.
The same difference applies the other way round: Plaguebearer Flesh is noticeably darker, much more saturated.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Plaguebearer Flesh on the colour wheel See Titan Buff on the colour wheel
All matches: Plaguebearer Flesh equivalents · Titan Buff equivalents