Before you cut your hair, have you tried colored dry shampoo?  I have not had RNY yet.  But I already have very thin hair up top and use brown dry shampoo every morning to help cover up my scalp.  It works WONDERS!!  Try it about $10 a can.  I use Batiste brand.  They have it walmart, online or at Ulta. They have blond and brown..use to have red but cannot find it anymore.

People use to stare at my thinning bald head before but not anymore!!!

Best invention for thinning hair every.  Or I think it is.

Bev