Hi, looks like nobody has chimed in on this one yet ...
The supplied wiring harnesses sometimes have conflicting wire colours which doesn't help the casual installer!
I generally don't trust them, I find supplied harnesses are usually under-specification as well.
Anyway, it's probably a generic harness so the colours might not have any meaning without the original instructions that came with the harness. A multimeter will help with testing to see how it's supposed to work.
Proper DRL operation should go like this:
"OFF" = OFF. No light at all.
"ON" = Variable.
Variable means:
- during daylight hours (when daylight is detected by car sensor, or when parker/headlights are turned off) operate at FULL brightness
- during darkness (when daylight is NOT detected, or when parker/headlights are ON) operate at REDUCED brightness
So, if these are proper DRLs, you'll have:
Positive connection (probably red)
Negative connection (probably black)
Parker light connection (possibly white or yellow)
Usually blue is used for high beam, but as above - no guarantees there! Suffice to say that 12V applied to one of the other 3 wires should dim the lights if they work as they ought to. They don't always ... it might be an idea to have a quick look inside that black box to see how that wiring might be arranged.