Hello, and welcome.
Bless you for rescuing this poor furbaby!
While it's good that she ate and had a bowel movement, the vomiting of the red and orange chunks, plus clear liquid is troubling. Since she was surviving outside, she could have eaten something that was poisonous or not made for ingestion. She could have been born with a serious medical condition that needs to be treated, like distemper (panleukopenia), or FIP (Feline Infectious Peritonitis), which are usually fatal, but sometimes can be cured if treated aggressively and early enough.
Because she's so young and you know nothing about her past health conditions, it would be advisable to have her seen in person by a vet as soon as possible. If your vet is closed now, you can take her to an ER vet center for evaluation, diagnosis and treatment.
If you have any other cats, keep her separated from them, since you're not sure of her health status.
I hope all will be well with this little one!