colorimetrically

The story

1. Proto-Indo-European*ḱel-
2. Proto-Indo-European*ḱélōs
3. Proto-Italic*kelōs
4. Old Latincolōs
5. Latincolor
6. Old Frenchcolor
7. Anglo-Normancolur
8. Middle Englishcolour
9. Englishcolor
10. Proto-Indo-European*med-
11. Proto-Indo-European*meh₁-
12. Ancient Greekμέτρον (métron)
13. Ancient Greekμετρῐκός (metrĭkós)
14. Ancient Greekμέτρον (métron)
15. Latinmetrum
16. Latinmetricus
17. Englishcolorimetric
18. Proto-Indo-European*h₂el-
19. Proto-Indo-European*h₂élisder.?
20. Proto-Indo-European*leyg-
21. Proto-Germanic*līką
22. English todaycolorimetrically

From colorimetric + -ally.