Rear Window Washer failure?

[04Yukon]

Any suggestions on how to pursue this? My rear window washer simply does not work. It squirted some blue sludge and that's it. I guess it's clogged, but I never saw it work once since new. The driver info center never gave a low washer message, either.

 

I filled the reservoir and the fronts are fine. I let it pump to the rear for a solid minute and all I'm getting is a dry wipe.

 

Thanks for the tips.