This painting activity is great for memory care communities. Below are some pictures of paint scrape art I have done with residents in a community I worked in.
In this first one, get out canvas or cardstock, paint brushes, and acrylic paints. Then have the resident pick several paint colors that they like. You put dots of paint on the page in a random pattern. Then instruct the resident to move the paint around the page to fill in the white spots.
In these two pictures below, you need paints, cardstock or canvas, and something to scrape with (a wide foam brush or an old gift card works well). Have the resident pick several paint colors that they like. Then you put dots of paint on one side of the page. Have the resident take the scrapper and move from one edge of the page to the next. If need be you can do this hand over hand as well.
This blog has also has a good description of how you do paint scraping.