Tundra Taupe vs 7K Russian Tan

How close are they?

ΔE 9.9, close: similar, with a visible difference side by side. 7K Russian Tan is a little lighter, warmer than Tundra Taupe.

Can I use 7K Russian Tan instead of Tundra Taupe?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). 7K Russian Tan is a little lighter, warmer than Tundra Taupe.

Can I use Tundra Taupe instead of 7K Russian Tan?

The same difference applies the other way round: Tundra Taupe is a little darker, cooler.

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.