Viability Dye for the Canto

Dear Flowers,
I have one more question with regards to the CFC(Cytokine Flow Cytometry) using the
Canto. What would be the best viability dye that can be used in a Canto. I would like to
use the Blue Laser Detector A (far red, detector for PE-Cy7) as I have other colors
filling up other channels. I am looking for a viability dye that can be collected in this
detector and also pose no problems with perm/fix protocols. 
I request all of you to suggest me a useful viability dye for the FACS canto. I tried
using the 7-AAD but could not quite differentiate the dead cells as I guess the perm
procedure is causing a problem.
Waiting for your suggestions.
Thanks,
Vijay