Using pretty shades of acrylic paints could potentially save you money if you've already got them laying around the house, but one must first investigate whether these paints are safe for our nails or not. Then there's the matter of their pigmentation. Nail polishes aren't meant to last forever, but traditional paints are manufactured to last.
According to Painting With You, many acrylic paints are non-toxic, meaning they won't harm you if put on your nail or skin. If you can find non-toxic varieties, acrylic paints should be fine to wear. In fact, they simply recommend always putting on a coat or two of a clear base before the paint to ensure it comes off easily and doesn't stain your skin or nails. They further note that acrylic paint is cheaper and comes in larger containers than most nail polishes, so you can save money.
If you don't choose a non-toxic variety, you could expose the body to lead, copper, cobalt, manganese, and chromium, among other toxic metals (via PaintTopics). So pay special attention to the paints you're buying if you're using them for this purpose. Moreover, since they're not made for nail use, they may not apply evenly. With some work, they typically smooth out.
So using acrylic paint is perfectly valid, and PaintTopics even notes that this type of paint is great for nail art. Have fun with it (and be safe)!
