Yellow Head

Hi, please can some one explain why my white chicken (i think she is an amber) head feathers have gone yellow colour, She is one of four chooks and we only got them in september, they are all happy and I think they are moulting, owing to the amount of feathers floating round the garden. Two days ago her head looked quite wet, but she does like going going under the bushes, she is eating well and I think she is laying (she kees going into the nest box). Thank you.   

I have heard that white hens can show the yellow pigment that colours egg yolks in their feathers when they are ready to lay- not sure if this is an old wives tale or not but my white hen is looking a bit yellow all over!