ΔE 17.9, loose: different enough that you should pick on purpose. Red Glaze is noticeably lighter, much more saturated, cooler than Cadian Fleshtone. They are different kinds of paint: Citadel Cadian Fleshtone is an opaque base/layer paint and Two Thin Coats Red Glaze is an ink, glaze or transparent 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 18). Red Glaze is noticeably lighter, much more saturated, cooler than Cadian Fleshtone. They are different kinds of paint.
The same difference applies the other way round: Cadian Fleshtone is noticeably darker, much more muted, warmer.
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 Cadian Fleshtone on the colour wheel See Red Glaze on the colour wheel
All matches: Cadian Fleshtone equivalents · Red Glaze equivalents