Buttons colors for a web app [duplicate]

we are designing a web app focused on managing projects for every kind of enterprises (like Trello, Asana, etc). We have several functional buttons in the same area (add file, add task, add subtask, see documents, add new project, add new message, and a lot of more...). I am using for a positive action (add) the green color and for a negative action the red (the background is white and the font has different grey tonalities).

My doubt is for the rest of actions: should I play with more colors for distinguish the buttons between them or should I use only the green and red in the whole application? What rules can I follow?

Thanks and regardds, Alejandro.