My lenses may have been fitted the wrong way round. They are orange but that is not the problem. They are asymetrical, the curvature on each side is not the same. Which is the correct way round to fit.

I can only go by the make that I have fitted on my car--"STARS". On these indicator units there are 2 screws that hold the orange cover to the body of the lamp--1 screw is recessed into the cover whilst the other screw has a small stand up 'land' that it screws through. The RECESSED screw should be on the OUTSIDE of the car. Fitting the cover this way, the curve of the cover follows the curve of the front panel.

Thanks for info. I can see what you say is correct. My problem was the white plastic bulb holder as this has to be the right way round as well, the lugs for the lens screws have to align.