Polarity on LED SMT Components

Is there some standard that governs how polarity marks are used to denote orientation on a SMT LED component, PCB silkscreen, and on assembly drawings? Examples: Cathode or Anode in the case of an LED, Pin 1 on an IC, must the mark be visible from the top, etc. The following is included for background: I have been an SMT Manufacturing engineer for over 10 years. I program Pick & Place equipment along with SMT process debug. Within the past year I have been struggling with SMT LED orientations. I know how to read a polarity mark and look at a data sheet but I have been having issues with SMT LEDs. I started running a new assembly and it had two different color LEDs. The LED's were placed on the PCB in the same orientation according to the silkscreen mark on the PCB and the customer assembly drawing. I had not looked up the data sheet or looked at the assembly schematic. There were no questions with the assembly with regards to the LED orientation during visual and automated inspection until ICT says one LED is backwards on every PCB. I look at all the information and cannot understand why. Based on the data sheet for each LED, the polarity mark denoted the anode on one LED and the cathode on the other LED. Needless to say I was confused. Everything in my training and experience told me both LEDs were placed correctly, until I looked at the data sheets. Since the above described incident, there have been dozens of cases in which an LED had been placed backwards due to the polarity mark being misread. Historically, I have not had issues with SMT LED polarity. It seems as if LED polarity marks have become ambiguous and highly dependent on application and manufacturer during the past year. Can you offer assistance? Thanks for you time.