Should I inform the graduate admissions committees (of all the Universities I have applied to) of the acceptance of one of my papers?
Ben Norris' comment is right.  I will elaborate a bit.

As an undergrad, having an accepted paper is much more significant than having a rejected paper (i.e., the net perception is very positive even if they learn about both).  Furthermore, rejection is probably temporary (you'll probably resubmit after improving it and it may get accepted) whereas acceptance is permanent.

Tell them about the acceptance.  If they ask directly, tell them about the rejection.  But there is no reason to feel obligated to broadcast a paper's rejection.  The people reviewing your application certainly don't list their paper rejections when they apply for a job or a grant!