ΔE 15.6, loose: different enough that you should pick on purpose. Light Turquois (Phthalo) is noticeably darker, warmer than Royal Cloak.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Light Turquois (Phthalo) is noticeably darker, warmer than Royal Cloak.
The same difference applies the other way round: Royal Cloak 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.
See Royal Cloak on the colour wheel See Light Turquois (Phthalo) on the colour wheel
All matches: Royal Cloak equivalents · Light Turquois (Phthalo) equivalents