This is what it has to say about red/brown droppings:
"When you find reddish or dark-brown to black droppings, there may be blood causing this discolouration if you didn't give red food to your bird before. For example red beet or cherries as well as some kinds of berries temporarily lead to reddish droppings. In case the droppings remain discoloured in the described way for a longer period, it's better to contact a vet and tell him about it."
My little guy's droppings are tan/beige on the days he doesn't eat his vegetables but only eats pellets and a little seed. But it is definitely related to diet. Usually he eats loads of veggies and the droppings are green. If you haven't changed diet recently, I might be concerned.