Capillary refill time sounds a tad technical for most of us, but in reality it is a very basic test. The process involves pressing on your pony’s gums until they go a white-ish colour. Then remove your finger and they should return to healthy salmon pink.
If it takes more than two seconds for the salmon pink colour to return after pressure then this can indicate dehydration, shock, or toxicosis (an overload of toxins in your pony’s system) – all mean you need to call your vet, right now!