ΔE 15.6, loose: different enough that you should pick on purpose. Deep Sky Blue is a little lighter, cooler than Pale Indigo.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Deep Sky Blue is a little lighter, cooler than Pale Indigo.
The same difference applies the other way round: Pale Indigo is a little darker, 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.
See Pale Indigo on the colour wheel See Deep Sky Blue on the colour wheel
All matches: Pale Indigo equivalents · Deep Sky Blue equivalents