Boone Tan vs Phalanx Yellow

How close are they?

ΔE 41.9, loose: different enough that you should pick on purpose. Phalanx Yellow is a little lighter, much more saturated, cooler than Boone Tan.

Can I use Phalanx Yellow instead of Boone Tan?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 42). Phalanx Yellow is a little lighter, much more saturated, cooler than Boone Tan.

Can I use Boone Tan instead of Phalanx Yellow?

The same difference applies the other way round: Boone Tan is a little darker, much 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.