How can I get yellow stains out of dish towels?
You can try Clorox if they're bleach safe towels or Oxi Clean works pretty good on colors. If the stains still won't come out, I'd just use them anyhow. You can always buy some new ones for relatively cheap and use the stained ones as dusting rags.
try soaking in bleach water---you must use cold water--no hot water, hot water changes the chemical reatcion of the bleach ,,if they won't brighten it's cause they are too old or they are already tainted by hot-water bleaching