The paint marks are usually put there by a utility company or a company that is contracted to mark out utility services. Each color represents a specific utility and when the color is painted on the ground, it alerts all construction workers that they are working within the boundaries of a specific utility. Obviously, extreme care needs to be taken around any utility to prevent accidents from happening that could cause an injury or death. Any time work is to be performed in the area, the contractor hired to perform the work must call for a mark out to ensure the area they will be working in has all the utilities clearly marked.
The color code of the utilities is a universal color code and it is the same nationwide. Even if a homeowner is performing work around the house, particularly when there will be digging such as installing a fence or building a deck, it is a good practice to call for a mark out. It is NOT safe to assume that all utilities are in the streets or sidewalk. There are many cases where utilities travel through side and back yards and most home owners are unaware of it. The direct number for an emergency mark out is 811.