I fell into one of my own favorite traps last week: the dreaded LED footprint mess.
I designed a board based on the Microchip PIC32 - it's a ChipKIT Arduino-compatible board - that has a number of RGB LEDs. on it. I used Part number LTST-C19HE1WT, from Lite-On. Their datasheet is easy to find, and they put the footprint information right up front, just the way we like it.
Almost all is well, but I somehow missed taking my own advice, and I didn't double check the footprint.The footprint I used is more or less 180 degrees off from this one. The common Anode is still on pin 4, but the numbering is different. It's got pin one in the same place, then pin two is in the lower left. Pin 3 is on the same place, and pin 4 is on the upper right. That's the conventional pin numbering order.
Fortunately, the fix won't require any mod wires. If I rotate the LEDs 180 degrees, the anode will be in the right spot. All I'll need to do is adjust my software for the correct R, G, and B pin locations.