Just looking at older posts, so not sure if you already got this but I'll answer for anyone else that runs across this post.
vManage config:
1. In Configuration/Policies/Centralized Policy/Custom Options/Lists/Data Prefix, create a Data Prefix list with all your networks or just list RFC1918 addresses, we'll call it DPL-LAN_SUBNETS.
2. In Configuration/Policies/Centralized Policy/Custom Options/Lists/SLA Class, create an SLA Class list or use a predefined list, let's use the predefined Voice-And-Video list.
3. In Configuration/Policies/Centralized Policy, create the AAR Policy. Add a Sequence Type, then Sequence Rule. For the Match Condition, select Source Data Prefix and select DPL-LAN_SUBNETS that we created earlier. Click Action, SLA Class and select Voice-And-Video. Under Preferred Color, select your ISP#1. Now, Select feature Backup SLA Preferred Color and add the color of ISP#2.
4. Make sure you have your Centralized Policy template attached to all Device Templates. That's it.
This policy will constantly check ISP#1 with the SLA by pinging external Cisco IP and if the circuit ever passes the threshold of the SLA, then all your traffic will utilize the Backup color.
Please respond if you have any more questions and obviously, for those that are new, I can provide more details as well.