If it's AC, a capacitor might be usable (in part). At low voltages, you'd need kind of a big cap though, several uF. Film capacitors not so practical there; ceramics plenty available in such ratings, albeit relatively expensive just for lighting an LED. If this is DC then obviously this is irrelevant.
Note that there are two kinds of green LED: traditional old GaP greens have poor to terrible efficiency (particularly bad at low currents), and a ~2.2V Vf. The new kind is GaInN based, Vf ~ 3V just like blue LEDs, but green emission (which is achieved with, something about nanodots or a quantum well, I think?). Despite the higher voltage drop, the efficiency is so much better, plus efficacy (around green is the "brightest" color to human vision), that they are in all respects better.
And needless to say (from all the blue spots we burned in our eyes, mid-2000s onward), blues are usually quite high efficiency. Reds are reasonable too, in the classic AlGaAsP alloy; yellow and IR are in the same family too, with efficiency worsening as you go up in color. So, yellow is still alright, but green kinda sucks (note GaP is just AlGaAsP with Al and As turned to zero).
Speaking of efficacy: the eye curve is dropping off steeply in the red range. Deep red is quite a dim color to the eye. There's some advantage in skewing it even just a little orange. Such "high efficiency reds" are available. The color is very subtly orangish, enough that you'll probably never notice it short of a side-by-side comparison.
Interestingly, GaP and GaInN greens are noticeably different, GaP being just slightly yellowish, GaInN slightly cyanish. It's quite apparent, side by side; but no one's going to mistake either one for anything other than "green".
Anyways, for any kind of DC arrangement, the only thing you can do is, use multiple in series, or add a ground-return terminal and power converter.
The former might actually be a little feasible, but it depends. For sure it's the way to go for discrete LEDs on board, that you just need to stack up a bunch say for a background light, or to trace out a shape, or whatever. If they all need to be independent, that's harder to pull off in the same way, however. As for the converter, obviously that's not going to fly, not just for individual indicators.
Apparently there are some high-voltage LEDs, but I don't think anything is widely available outside of illumination? Saw that on bigclive the other day, some multichip solution, or maybe it's monolithic after all? A bunch of diodes wired in series, all clustered together acting as one big chip rated 24V. Also the faux filament stuff, lots of teeny chips wired in series, almost use it like glowing wire. Not sure you'd use either for indication though, and certainly not in colors (filtered LEDs give terrible washed out colors!).
If they're on most of the time, it might do to run them in series anyway, from a current source, and short out a few using a suitable switch (maybe a BJT across each respective diode, or set of diodes, that needs to be blanked?). The load is always the same, so the more LEDs turned out, the CCS drops the remainder, and the hotter it gets (instead of the same heat distributing over all the LEDs).
Or just add the 3.3-5V supply and run them all on that. Preferably with current-limiting drivers, very easy to do.
But these are getting very much towards design options. Whereas, if this is like replacing incandescents in an existing product, yeah, don't even worry about it really, it's still more efficient even with the resistor in there -- just try to stick the resistor somewhere it can dissipate its heat.
Tim
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