This may be handy for some LED based projects...thought I'd share, and also to prove I do use things out of my boxes of salvaged electrical components!
I had a box of unmarked LED's, most of them were obvious as to what color they were, but I had a pile of clear LED's that were unknown as to what color they were.
Since most LED's run on around 3v, I found some spare parts in my electronics boxes, 2 AA batteries, and made an LED tester.
The batteries are in series routed to an on-off slider switch, which is connected to a salvaged 2-prong computer connector that makes the ideal plug for LED leads.
I found a generic black box and stuffed it in there, cutting holes in the side for the on/off switch and test lead. The AA batteries should last quite awhile testing LEDs.
Sorry for the blurry pics, I should've switched camera to Macro mode...
Oh and most of those clears were unremarkable green's...not more rare blue or white, and not super brights.