Once upon a time artists did not merely paint. They made their own paints from purchased pigments and they stretched and prepared their own canvas and they made and painted their own frames. In the 2003 movie The Girl with the Pearl Earring there are some rich scenes of Vermeer and his model for the picture mixing paints including the infamous Vermeer blue.
When I was an undergraduate at the University of New Mexico majoring in fine arts we bought our paints but we stretched our canvases, coated them with rabbit skin glue that we prepared on a hot plate, and then applied gesso to finish the surface. It was in vogue at the time to not frame pictures. You painted the edges of the canvas as well as the front. Previously artists had made their own frames and some in my classes did.
Now you can buy any paint you want. No need to mix your own. And canvas comes pre-surfaced and pre-stretched.There is a huge business in manufactured frames, but framing costs are through the roof especially if you need a custom frame because of a custom size when you don't buy a pre-stretched canvas. So there is a return to the unframed painting with the painted edges, and a return to artists making their own frames.
I started doing my own basic floater frames this last year and painting them a basic black then I read that it was not unusual in the days of artists making their own frames to paint them to coordinate with the paintings they were for. And paintings of famous artists with the original hand made frames by the artist are highly valued. It is a frame made for the painting not to match the decor of the owner's living room. No doubt many were replaced so the decorator could have all ornate gold frames throughout the house. But after almost a year of experimenting with the no frame look I find pictures sell better with frames even if the buyer has every intention of replacing it. So why not have fun.
The two paintings above are sold. The frames are black on the inside and burnt orange on the outside. Then to compliment the painting one has purple on the facing edge and the other gold. I plan to get some more acrylic paints to coordinate with the watercolors I use in my paintings so I can further experiment with the matching frame concept. I am already stretching my own canvases (prepared already) so I can have some unique sizes to fit my subjects. I doubt I will go back to mixing my own egg tempera but I do know how. I learned that in high school.