On Thursday, April 12, 2018 at 8:19:07 AM UTC-7, Terry Schwartz wrote:
That can easily be addressed by using two LEDs in parallel, in opposite polarity.

At the risk of pointing out the obvious, an incandescent bulb doesn't care which end is positive. An LED on the other hand..................

One variant is to get a bicolor LED; these are usually red forward, green reverse biased.
It's better not to tease the R/G colorblind population, though, and
a white LED pair, behind + and - shaped windows, would be a better indicator.