My leopard puffer changes color from a very dark color. .

[cbseven]

to his "normal" yellow. Sometimes I see him on the bottom of the tank just sitting there but he is really dark ( almost black ) then he will move around and turn a lighter color in like under 5 seconds.
And he will changes colors randomly. Ive had him for 1 day and I havent been able to get him to eat. But I guess that parts common.

[hc8719]

i know my black kuhli loaches, and pleco getter lighter or darker depending on how much they eat, its usually the darker the healthier i beleive, for my fish anyways. that doesnt mean dont feed a dark fish, i dont have any scientific evidence, all fish should be fed everyday though.

puffers only eat live foods i beleive, so if your trying to feed them flakes, it wont work, petsmart even told me that dragon gobies, needlefish, and BGKs would eat flakes, well they wont.

you could use frozen, (actually you need to, they'll know freeze dried and wont eat it, besides frozen is cheaper per ounce too) and if you have a strong enough current in the tank, dupe the puffer into thinking its alive.

blackworms are another possibility for live food, you have to order them online though

EDIT: just remembered, fish changing colors could also be a sign of stress...

[penpitt]

It could just be normal while he acclimates to his new surroundings but if you can answer a few questions we might be able to determine if there is something else wrong.
What size tank is he in and what other tankmates?
Is the tank cycled and what are the water parameters?
Is he in a freshwater setup or a brackish setup?