The yellow colour of egg yolk is due to the pigment

The yellow colour of egg yolk is due to the pigment Xanthophyll.
Pigments that impart a yellow or orange color to egg yolk belong to an oxycarotenoid group called xanthophylls.
The most important xanthophylls for egg yolk coloration are zeaxanthin and lutein. The former is causing egg yolks to be more orange-red, while lutein imparts a more yellow hue.