Red Tile vs Viper Brown

How close are they?

ΔE 9.4, close: similar, with a visible difference side by side. Viper Brown is a little lighter, more muted than Red Tile.

Can I use Viper Brown instead of Red Tile?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Viper Brown is a little lighter, more muted than Red Tile.

Can I use Red Tile instead of Viper Brown?

The same difference applies the other way round: Red Tile is a little darker, more saturated.

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.