No, there is no bleeding of ink on the back (anyway, the ink used are water-proof, so unless you use of solvents), and on a normal note, the serial number appears deep red. I tried to scan two notes, one normal red beside the orange serial. The difference is noticeable, but not very strong (it's better when eyeballed). I's much like the orange vs red serial numbers on the CTC-S4 serie.