Elder Flower vs Cyber Pink

How close are they?

ΔE 15.7, loose: different enough that you should pick on purpose. Cyber Pink is a little lighter, much more saturated than Elder Flower.

Can I use Cyber Pink instead of Elder Flower?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Cyber Pink is a little lighter, much more saturated than Elder Flower.

Can I use Elder Flower instead of Cyber Pink?

The same difference applies the other way round: Elder Flower is a little darker, much more muted.

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.