as George Bernard Shaw would say, we may be two people divided by a common language. It looks like you have fresh plaster or concrete that may need to be sealed for waterproofing by a primer or base coat. The porous nature of the plaster (stucco or concrete) will take lots of paint so Plain color under coat or base could save you money on the more colorful topcoat which will last longer if you use the right primer. These all can be water based or oil based but mixing the two will cause problems. Ask you paint supplier for the best way to use their product. Be sure to tell them what the building material is so you get the right kind of paint. The climate will matter too. In damp climates you may want a mildew resistant primer or in dry hot climate one with UV protectorants to resist fading. Hope this all makes sense.