According to "Eric King's Guide To Psychedelic Rock Concert Posters", this poster was printed just once...all NR 8 posters are originals.  Eric has drawn this conclusion after several interviews with artist, Victor Moscoso.  We have no
particular reason to doubt this, but we certainly have two distinct variations of this poster. 

This original/first print poster (we will call it Type A) has noticeably lighter colors than the Type B original.  The pink is a pale pink, and the blue is a "baby blue".  It is also slightly longer than the Type B (1/8" or so).

This original/first print poster (we will call it Type B) has noticeably darker  colors than the Type A original.  The pink is more intense, a magenta, and the blue is deeper, a royal blue. 

We have seen no posters that transition these two color combinations, so we do not think that the variations were caused by strong/weak ink within the print run.  We think it is a separate run using different inks, and cut at a different length. We rarely see the Type A poster, and have priced it accordingly.