Cadian Fleshtone vs Dark Rose Tan

How close are they?

ΔE 17.3, loose: different enough that you should pick on purpose. Dark Rose Tan is a little darker, cooler than Cadian Fleshtone.

Can I use Dark Rose Tan instead of Cadian Fleshtone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Dark Rose Tan is a little darker, cooler than Cadian Fleshtone.

Can I use Cadian Fleshtone instead of Dark Rose Tan?

The same difference applies the other way round: Cadian Fleshtone is a little lighter, 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.