Yes, the toads are the ones who make the long, loud whistling call in early spring (then they depart the pond & live in & around the garden) Their skin is more 'bumpy' than a frog, females are definitely larger than the males, and they come in a variety of colors/shades.
These are all toads (and two large frog tadpoles):
Bullfrogs & green frogs also come in a variety of colors ranging from really green to more brownish. Their skin is smoother & less bumpy than the toads. Bullfrogs (at least in my pond) tend to get darker as they get bigger & mature out WAY larger than the green frogs, but the two are remarkably similar when they are not full grown. The one definitive way to tell them apart is to look for the two 'ridges' running down either side of their back (dorsolateral folds, to get technical) Green frogs have them. Bullfrogs do not.
Young bullfrogs (ridge around the tympanum - eardrum - but not down the back):
Adult bullfrog:
Green frogs (note the very obvious ridges on the back):
Those ridges are obvious from the very beginning, as shown by this little green frog still sporting a 'tadpole butt'!