I had this happen on one my quilts a couple years ago but it was a deep red that bled onto the white. I didn't catch it till after it had gone into the dryer too so thought it was a lost cause but someone here said just throw it back into the washer with a color catcher and it should take out the red. It did and I was never so happy as when it came out of the dryer the second time with no bleeding of red.
Haven't tried the Dawn method but will keep that in mind for future moments.