Some years ago, I used to use a procedure for N,O-permethylation of peptides. This involved warming DMSO with NaH to form a strong base. Completion of the reaction was assessed by spotting a few uL of the solution onto a few crystals of triphenylmethane. A bright red coloration indicated the successful formation of the base, which abstracted a H radical to leave the red Trityl radical.
You may have a similar reaction here.