As far as african bullfrogs go, the dwarves seem to retain a lot more color into adulthood than the giants.

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The first of these is an adult dwarf the second is an adult giant. Note how the dwarf maintains some of its pattern into adulthood while the giants fades.
Also, dwarves tend to have stronger coloration around the front legs, belly, face and throat.

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While they don't look a WHOLE lot different as babies, they're pretty easy to tell apart if you know what to look for.
Baby giants are more colorful than the baby dwarves.


Hope this helped at least a little!!

(PS I claim no ownership of any of these images. All belong to their respective owners. Obtained through Google images search.)