Welcome to the Jackson's club!
They are such wonderly gentle critters and sweet is a perfect description
If you have a vet who knows how to treat chams, such as Dr Ivan Alfonso who became a vet because he loves chams, then a vet visit would be an excellent idea.
A fresh fecal sample should be brought to determine if he has internal parasites sapping his strength and affecting his health.
If he is green, then he is older than 4 or 5 months, as Jackson's are a mottled brown and tan camoflauge pattern at that age.
He will see your Veiled as a threat, so he should have a barrier to keep them from seeing each other.
Very important for Jackson's are the right temperatures and humidity.
I don't think ever ever seen one in a store who wasn't somewhat dehydrated from too little water and too much heat.
Most Jackson's are shy, so it can be difficult to get them to drink enough if you don't realize this.
Long, relatively frequent mistings are the answer to that.
If you have an AquaZamp or MistKing system, then you'll have an easy time keeping him well hydrated.
You can give him some long mistings and see if that perks him up more, as that might be the problem.
It is probably much too hot where you are for outdoor time during the day but you may get cool enough temps early in the AM to sneak in a bit of real sunlight.
Another thing to keep in mind is that the supplement schedule for your Veiled is about twice as much as your new Jackson's needs.
Calcium without D3 or phosphorus can be used on most feedings, or every other feeding if you like but you must only use a multivitamin just 1x a month and use calcium with D3 only 1x a month, or problems will occur.
Here is the forums page on Jackson's
https://www.chameleonforums.com/care/caresheets/jacksons/ which is well worth reading, as their temperature requirements and supplementing differs from Veiled and Panther chams.
Anyone interested can see just a few of my Jackson's here
https://www.chameleonforums.com/young-cbb-jacksons-females-133320/
