Lokay, this is a guess since we can't see the light, but I think the reason that you don't have turn signals is becuase you have power to ground...
Here is a suggestion to see how it works and I would do these one at a time to use the process of elimination:
You have a tail light, so I say leave brown & red
All are listed bike side wire first.
Then, l/g & blue and B/W & B; then test you turn signals and see if one of them comes on. If it does not, then try B/W with the other B wire. Retest.
Repeat with the B & Y and B/W & B - perform same as above
Then try W/B & W
I think that Red is the tail, Blue and Yellow are the Turn signals and White is your brake.
This is the best that I can do with out seeing the back of the light assembly and seeing where the actual wires are coming of the assembly.
Sorry I can't be more help.