It seems like before there was only yellow pvc used for electrical. But now white pvc is becoming widely available next to yellow also apparently for electrical usage. I have asked the sales people at various places about the differences only to hear inconsistent answers like "only difference is the color" or "yellow is imperial, white is metric". Does anyone know what the actual differences are and when to prefer one over the other?

 

I use the white when it's on the surface, easier to paint.

 

Other than colour I don't think there's any real difference.

 

I've also seen white water pipe and fittings.

A little searching on a couple of sites suggests -

Household water supply    -   Artic Blue

Electrical wiring & Telephone Cable   -  Light Yellow

Drain, Waste or Vent   -  White (PVC)  Black (ABS)

Agricultural   -   Grey

Chemical Products  - Dark Grey

but the above doesn't seem to be absolute except in a few countries' codes