>> So the question is this: What LED would you use to get the
> most noticeable indication from 5 volts through a 4K7?

I bought a bag of HLMP1385 many years ago. 3mm diffused
red that are more than OK as indicators at 1mA

Although they're obsolete-ish, Digikey and Mouser still list them,
as High Efficiency, and I can vouch for that. Would be surprised
if something similar isn't now available from HP, Kingbright etc

Maybe search for Efficiency rather than Brightness

As noted, considering the Vf of the diode, you would be able to
get closer to the pin current limit with a smaller resistor (3k6 ?)
whilst delivering more current to the LED

Joe
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