ΔE 15.2, loose: different enough that you should pick on purpose. Tallarn Sand is noticeably darker, cooler than Brethil Blush.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Tallarn Sand is noticeably darker, cooler than Brethil Blush.
The same difference applies the other way round: Brethil Blush is noticeably 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.
See Brethil Blush on the colour wheel See Tallarn Sand on the colour wheel
All matches: Brethil Blush equivalents · Tallarn Sand equivalents