Yellow color on my blue contacts after I took them out?

Question

They are normally a blue=ish tint and they were still blue but there was yellow on them. What causes this?

Answer 1

If you've been around a lot of smoke they can turn yellowish.

Answer 2

How old are they?

I don't know about you, but I wouldn't be putting them in my eyes anymore.  I've been wearing one contact for 3 weeks now because of an eye infection, and trust me, the headache is NOT worth it.