"are painted on" is correct and usable in written English.
You can use it when describing that something is painted or drawn on a surface. For example: "Bright colors are painted on the walls of the room."
For instance, a trio of gauges (including mph, tach, temperature, fuel) are always backlit, but the numbers themselves are painted on clear plastic.
Banners are painted on one side or on two sides of the same fabric or consist of two painted fabrics sewn together.
Bold New Age ones are painted on the walls and clusters of shimmering, five-pointed paper lanterns hang from the high ceiling.
It consists of fifteen paintings on nine panels; six of these are painted on both sides.
The altarpiece is composed of fifteen separate paintings on nine panels, six of which are painted on both sides.
Most of the paintings, save for a series of smaller works titled "Valley Forge, 1777," are painted on an unmodulated background of warm or cool black.
Some are painted on cigar box lids.
The set is inspired by commedia dell'arte: stage curtains and scrolls are painted on the wall.
White numerals are painted on the trees as reminders for when their next turn comes up.
Smaller and clearer images like airplanes, fedoras and seashells are painted on top.
The plot summary and a floor plan are painted on huge white sheets.
