Egg Yolks

What color is the yolk of an egg?  That's what I thought too.  This morning for breakfast Michelle made hard-boiled eggs.  Looked like a hard-boiled egg from the outside.  When I cut into it it was white.  All the way through.  A white yolk.  Perfectly normal, I'm assured.  Just not expected.  It tasted good.  -Shauen