Help identifying a replacement for this discontinued LED, please?
Physical measurements
Are obviously the most important parameter. A 3.2mm lens with 5mm pitch is something of an oddball part. The most common lens sizes are 3mm and 5mm. The pitch is almost always 2,54mm (0.1'').
Depending on how critical this is, maybe you can use a 3mm or 5mm lens part and widen the pitch by using through-hole &quot;lead bender&quot; tool. Or go look for 5mm pitch parts, but that will narrow down your options dramatically.
This is where you may get urges to go have a polite conversation with the person who specified such an exotic part to begin with... :)

Luminous intensity (candela)
The main issue with your part is that it's so old - you won't find LEDs with just 10mcd today. Meaning that a replacement part might shine some hundred times brighter! You can compensate for this by changing the series resistor though. And end up drawing far less current than your original part.
(In some rare cases this might actually cause EMC issues since more current = more robust to noise. If you have to change the series resistor from 1k to several 100k, then it may affect EMC.)

Forward voltage and current
Forward voltage affects forward current and thereby brightness as well. If you mean to switch from orange to blue then you'll likely get a higher forward voltage too. This can be an issue in case you supply it with 3V3, because some LEDs have too high forward voltage for that!
While forward voltage will vary a lot between parts, the optimal forward current is almost always 20mA, it's an industry de facto reference current. If you look at your current part, it specifies all conditions with IF = 20mA - meaning forward current. Lower current means lower luminous intensity (and it's not necessarily a linear equation).
Again, you can experiment with the series resistor to find the optimal value.

View angle
It's typically somewhere around 30 dgr to 90 dgr.

Lens type Clear or diffused.


The other parameters like wavelength are probably not critical in your case. If the specification is &quot;blue&quot; then just look for that. For manufacturing, soldering temperatures matter a lot, it's quite easy to damage LEDs if given too much heat, but that's more of a parameter that you need to inform the assembly contractor about. Be especially careful about this if you intend to buy from fishy manufacturers nobody has heard of.