Light Transport
Flight Crew Air Transport Pilot (ATP)
Distraction; Confusion; Communication Breakdown; Situational Awareness
Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Environment - Non Weather Related; Airport
In EWR; upon taxi out we received the instructions from Ramp Control to taxi B short of K and contact Ground. Upon contacting Ground Control they instructed us to taxi B short of E for [Runway] 4L; we complied and continued taxiing. We were then issued new instructions to taxi S; A then PA to Runway 4L. I taxied right on to what I thought was S; but after making the turn we both noticed that we had actually turned onto Taxiway RG instead.  We then made the left turn onto A and continued on our instructions without further incident and Ground Control did not comment on any wrongdoing. I believe the taxiway confusion first began with the initial change from getting a new taxi route from ATC to join A from parallel B. Usually going to [Runway] 4L; the aircraft would be given Taxiways B to D; but with taxiway construction; parts of B and D were unusable.  More importantly though were the very confusing taxiway signage located at the intersections of Taxiways B; S; J and RG; where they have a direction sign for S that looks like it is actually pointing toward Taxiway RG; which had caused most of the confusion on my part.
An air carrier Captain cleared to taxi EWR Taxiways B; S; A; to Runway 4L; turned onto RG then A because the signage at the intersection of Taxiways B; S; J; RG misleads one to see RG as S.