Plastic sheathing and masking tape was not available at the end of the painting project for whatever reason, I have no idea, but you have a Paint Brush that if not cared for will eventually dry up. Last solution that works well, is to take a sopping wet rag, wrapping the Paint Brush up like that burrito you missed wrapping up earlier. This will buy you some time until either you use the paint brush again, or you can properly clean it. Will the color fade? Now this is a very broad question with various answers. Hair color fading is due to many factors. First of which is, the ability of the hair to hold hair color. We call this porosity. If the hair is overly porous it will have a problem holding hair color. There are ways a stylist can usually alleviate this problem. Once in a while the hair is so damaged it absolutely impossible for the hair to hold color. Your stylist should always have the skills to evaluate these situations, and recommend certain conditioning treatments to bring the hair back to a normal porosity. Can you feel the rhythm in repeating some color or combination?
Another idea keeping Paint Brush moist until the next paint coat is applied (but not leaving for extended periods) is leaving Brush in container, wrapping top with plastic, sticking handle out the top, and taping around the can. This resembles the Maxwell House Coffee Container mentioned earlier. If plastic and masking tape is still not available, and time between coats is not very long, take that sopping wet rag, draping over the top of paint bucket with Paint Brush still in it. This technique works best when using Latex waterborne paints. Vinyl is a cousin to the tough plastic used for upholstery and floor tiles, but it comes thinned with water ready for you to brush, roll or spray on. The label on the can may say vinyl, vinyl emulsion, polyvinyl acetate or PVA. Step five: pick your colors and start applying them to your penciled outlined images...make sure to mix the paints with a little Galkyd. Painting right out the tube is probably a bad idea, and it'll take forever to dry. Mix the Galkyd pretty evenly with the paint until you reach your desired thickness of paint. Less Galkyd keeps the paint thick. More makes it thinner. A safe start for a painting subject is a still life, like a bowl of fruit. No matter what you do...within reason...it'll look cool. You do not have to make a twig brown or an apple red just because nature says so. Use your imagination. Do something different. Collectors over time like to watch you evolve painting by painting anyway. So don't worry if your first painting stinks in your mind. It'll be interesting later once you're great. And by the way, most famous paintings have an under drawing, so they've used this layout technique I mention above. Sorry to tell you, most inspired paintings were planned out with pencil first. They did not happen spontaneously. They were built logically and in a defined order so that the end result looks right. No single product can do all these things. There are several types, all available under a variety of trade names. The trade names are, to put it kindly, confusing. For example, two brands of the new paints use "rubber" in their trade names, yet neither is a rubber-latex paint and each is actually an entirely different type of paint from the other. To get the right paint you have to read the fine print on the label and find out what is actually inside the can.