Tallarn Sand vs Dune Shadow

How close are they?

ΔE 16.8, loose: different enough that you should pick on purpose. Dune Shadow is a little lighter, more saturated, cooler than Tallarn Sand.

Can I use Dune Shadow instead of Tallarn Sand?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Dune Shadow is a little lighter, more saturated, cooler than Tallarn Sand.

Can I use Tallarn Sand instead of Dune Shadow?

The same difference applies the other way round: Tallarn Sand is a little darker, 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.