Hi,
First, thanks for the great lib!

The structure of the wiki page on Delta E is not very clear but it still states that Delta E was defined by the CIE. There are various versions of the metric (76, 94, 2000), each coming with additional corrections.

The implementation of Delta E in chroma.js is that of CMC l:c which was defined by the "Colour Measurement Committee of the Society of Dyers and Colourists", not the CIE. So, even though it is defined as a subsection of the Delta E section on wikipedia, does not seem to be a Delta E metric (and the non commutability of the arguments is a tell of that).

@Offirmo proposed an implementation of Delta E 94 in #127. I implemented Delta E 2000 there (see the deltaE_lab function), albeit in R, but it should not be very hard to convert to js. It is checked against the data in the paper by Sharma et al 2005 and is correct.

I would suggest using one of those as chroma.deltaE and redefining the current deltaE as chroma.CMClc.

Thanks in advance!