Elemental Bolt vs Phthalo Green (Blue Shade)

How close are they?

ΔE 17.7, loose: different enough that you should pick on purpose. Phthalo Green (Blue Shade) is noticeably darker, warmer than Elemental Bolt.

Can I use Phthalo Green (Blue Shade) instead of Elemental Bolt?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Phthalo Green (Blue Shade) is noticeably darker, warmer than Elemental Bolt.

Can I use Elemental Bolt instead of Phthalo Green (Blue Shade)?

The same difference applies the other way round: Elemental Bolt is noticeably lighter, 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.