Kitten vomiting clear white foam?

Yesterday night my kitten began to vomit this clear liquid with a thin layer of white foam at the top. The morning came and it seemed he was fine except as night approached he began to vomit once again. This time however, he pooped this clear liquid. While his vomit yesterday had this green tint to it (and is now just clear) his poop also had this very faint brown tint to the liquid.

He's not acting strangely, he's not lethargic. He's been outside now a few times. Could eating a plant or some kind of bug from outside cause this? There's also been a change in his diet and while he's eaten this food before, it was never just solely this brand until recently. He hasn't peed either despite having a full bowl of water.

Thank you

Your kitten needs to see a vet. Yes, it's certainly possible for him to have eaten a poisonous plant or gotten into something toxic. The excessive drinking without urinating is concerning as it could mean he is trying to clear something from his body.

How is his appetite? Are his gums pink or white?

So, he doesn't drink excessively. It's just weird that he hasn't peed despite having constant available water. His gums are pink and he's playing up a storm like usual.

(Sorry, I'm just really worried)

His appetite is normal.

Typically with bomitinvvominting clear/foam it's a sign that the stomach is empty. I always worry when a cat, but especially a kitten has outdoor access and is allowed to roam. There are a lot of things they can get into.

Good that his appetite is normal and he is playing.

What is his feeding schedule like? What food and how much do you feed?

You still need to keep a close eye on him (I know you are!) as he could have eaten something toxic or could have eaten a foreign object that is causing stomach upset.

So he mainly eats dry food because wet food makes him gag and can disturb his bowel movements (asked the vet about it, said it was fine). We switched him to a new food recently that was slowly introduced before it became his primary food. He eats three times a day. I too don't like him outside and I watch him closely when he's out which is why I'm beginning to suspect that he probably ate a bug (maybe a one of those bugs that light up) because I've seen him toy with them constantly. He hasn't been allowed outside since yesterday and he's still behaving as he normally would.

Thank you for your responses. Really, they help calm me down.

Male cats really do fare better on an all wet diet.  Dry food can give them crystals.  You should discuss this with your vet.