It is normal in tortoises that are not well hydrated. In other words, its not a good sign. You need to soak your tortoise more often and for longer, up the ambient humidity a bit, and try to get more water into your tortoise. Wetting the food is one way to do it.
The white stuff is urates. It is the end product of protein metabolism in reptiles, and is normal - the consistency should be liquid or at the most, smudgy like toothpaste. If it is gritty or solid, your tortoise is dehydrated.
Green liquid-y poop usually means you need to feed more fiber. This means, more tortoise safe weeds, less grocery store greens. Also, if you haven't already, it's a good idea to bring a fecal sample to the vet to have them check for parasites. Before I got my microscope and taught myself how, I just took a stool sample to the local dog/cat vet to do a check in house. Cost $15. If it's positive for ova or parasites, then a reptile vet can help you determine proper dosage of Panacur.