Simple RGB LED/Pixel not working

Hello everybody,

I am a newbie to electronics and Arduino an have a problem with the following task.
We built this RGB LED boards in class and they all worked fine, but now i can't get them to work anymore.
The RGB LED board looks like this:



I connect the boards ground with Arduinos ground and the other 3 pins to pins 9, 10, and 11 of the Arduino. The setup looks like this:

I am using this Arduino sketch:

I am not sure if i am using the breadboard correctly. But using the same setup with a simple LED works just fine (of course i just have use 2 connections then..)
When testing the RGB LED board for resistance with a multimeter set to 200 ohm, i get all three colors to light up (not at the same time). So it seems like the RGB LED board is ok.
Still i can't get the Arduino board to light up the RGB LED.

Any ideas?



the part of the board where there is a wire ground jumper (top right of the solder-side photo) looks like it does not have enough solder to be reliable.
I can see two holes with the wire jumper that are just barely soldered.


i tested the connections on the board with a multimeter and everything seems fine.
i guess that means soldering is not the problem here (which btw looks wilder on the pic than in reality).