<p>I am looking to print an enclosure, which will have a PCB inside with some LED indicators. I was wondering if it is possible to 3D print the enclosure such that the following look can be achieved? What material and technique?</p>

<p>When LEDs are off, it looks something like this:</p>

<p><a href="https://i.stack.imgur.com/eUN2v.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/eUN2v.jpg" alt="enter image description here"></a></p>

<p>WHen the LED turns on, it looks like this (illuminated symbols):</p>

<p><a href="https://i.stack.imgur.com/X9GuC.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/X9GuC.jpg" alt="enter image description here"></a></p>

Achieving this with 3D printing would be quite difficult, and you might be better served by creating this effect some other way (I would personally recommend getting some inkjet transparencies and stacking a few layers together: an entirely black layer, and a few layers with the symbols in negative space).
One way that you
might
be able to achieve this using just a common FDM printer is to print the part face down, and printing just a single layer or two that covers the entire face, and then printing more layers that cover everything but the symbols. However, those symbols look small and detailed and you might not be able to reproduce such detail.