ΔE 5.7, very close: most people won’t see a difference side by side. Eidolon Purple Clear is a little lighter than Magecast Magenta.
Can I use Eidolon Purple Clear instead of Magecast Magenta?
Yes, for most jobs. Very close match (ΔE 6). Eidolon Purple Clear is a little lighter than Magecast Magenta.
Can I use Magecast Magenta instead of Eidolon Purple Clear?
The same difference applies the other way round: Magecast Magenta is a little darker.
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.