Is this color normal for this feather? (Senegal)

[DmG]

So I've 2 senegals, a female and male. I've them little over 8 years and this is the first time something like this, my male parrot his flying feather is yellow. Just 1 or 2, its been there for a while but have been curious if this normal?

Yellow Feather

My bird Sjaak

 

[Aspie_Aviphile]

I think you are supposed to take them to an avian vet when feathers change to yellow or brown, in case it's a liver or kidney problem.