Dug too deep? Should I be worried?

Actually, what happened was this...
About an hour or so in a 90 minute workout I noticed some red droplets hitting my sweat-guard. My 5 year old son was in the room playing around, and I told him to go get a mirror. I was starting to panic. Red droplets? I checked my nose... nothing. I checked my forehead... nothing.
Then it dawned on me.
I was wearing a red bandanna, and though I've had the thing for years, I must have never washed it because it was "bleeding out" now that it was drenched with sweat.
\*whew\*
Funny thing is that my first thought wasn't to immediately stop what I was doing, but to ask an easily distracted 5 year old to get me a mirror.