If you are caught up after a spot deny everything.
Just cause you have paint on you that matches whatever they are talking about does not mean you have to say anything.
They have to prove your case. Never admit anything. Say you found the paint somewhere prior to the arrest. Say it's for something else and the situation is very circumstantial.
If you have it plastic bagged in a regular bag you will look less suspicious as to having it at your waist when you get arrested.
This means the difference between graffiti implement and placing graffiti on property. Which leads to suspicions about your name, crew, ect.