How can I tell what glowy-ring buffs the enemy team currently has?

To my knowledge, all the following buffs have identical effects of glowing rings around the players' feet, as shown in this picture:

• Deploying a Buff Banner
• Deploying a Battalion's Backup
• Deploying a Concheror
• Playing a medicating melody with the Amputator
• Deploying Ubercharge with a quick-fix

If I could not see the source soldier/medic, what are some tell-tale signs I could easily/instantly recognize their buffs? Additionally, if I saw a buffed soldier coming in from a distance, how can I distinguish what his buff is?