Sounds like you just found something I bought about 4-5 yrs ago
If these are the same ones, I got a string at a K-mart in Texas (after christmas) cheap. I butchered mine for the leds
I haven't seen them for awhile, I was looking for more this year but haven't found them yet.
I connected a few together and ran them from batteries for somethings and even used them in toys and model cars for head lights and tail lights. Just kinda a normal LED but not real bright, not too dim either though. The light was all one piece, not a plastic difuser you could get off, more like led made into it.
I did try cutting the plastic ends off a few, I got a rough plastic with a colored fog type look. I sanded them with 600 and 1200 grit paper and polished them too. I was never very happy with them that way myself.
For some dumb reason instead of being round to fit a drilled hole nicely mine were kinda square flat sided and the reason I wanted to cut them. Also the plastic ends were a little long.
Over all I would say a nice Holiday lights, low power, long life, and a cheap source for colored LEDS for other uses too.
I nice side beneffit is you get the string with sockets, I cut it up and used it for my battery powered led stuff I made. Made wiring neat and easy, and bulbs can be replaced without soldering or other problems.