Bambu Labs Hotend LED Coloured Insert

Fortunately there is just over 10mm of space in front of the LEDs on the hotend, more than enough space to slide in something to add a bit of colour.

Printed with settings leaning towards this, though not as critical to get it all the way to glass-like.

You might have to change the thickness of the plate depending on what transparent filament you use, but just keep the tabs at 11.18mm to hold it in place.

Update: 04/23 Added a 1mm thick plate that works with solid color PETG, thanks to AH - Prusa i3 MK3S+ Kit@AHPrusai3MK3SKit trying it!

(For the purple I had to take the picture up close and out of focus because the camera didn't want to show this electric arc kind of ultraviloet colour of this Zi-Rui PETG Filament that they describe on Amazon as ‘Sparkly Glitter Purple, Shining Glow in The Dark Green’)