Mages

There are tales of worlds where magic is some amazing, earth-shattering thing all on its own. This is not one of those worlds.

Mage power is present in children as young as three years old. It can manifest any time between that age and death with seemingly no trigger, though the vast majority of mages are aware of their powers at least by puberty.
Mages are not genetic. Some countries and ethnicities have a higher overall mage rate than others, but there is no way to predict if a child will be a mage before they manifest the power.
There are three types of mages. Each has one singular power at their disposal.

Most Common: Chameleons

Mages who hold the power to change something's color. By touching an object and focusing their will on it, they can change the object's color to any color they can hold in their mind. Single colors are the easiest to hold, though dual and even triple color patterns are possible if the mage is disciplined.
For the most part, Chameleons don't have much advantage in everyday life. You can save a job some money on paint or dye, and your clothes always match, but beyond that it's seen as a party trick.

Second Common: Lightcallers

A valued part of society, Lightcallers possess the ability to create small pinpricks of light of varying intensity and duration. The lights they create attach themselves to a dust mote, so by containing the dust mote you contain the light for its duration. The vast majority of civilized towns use magelights for at least most of their lighting needs if not all.
Lightcallers have a physical limit to the number of lights they can make in a day, which can be increased with mental training. The duration of the lights, though, is set from the time they make their first one and there is nothing that can be done to change it.

The Rarest: Mirrors

At their most simple level, Mirrors consider a part of another living being and command "make that like mine". In reality, the talent is anything but simple and takes years of training to do much with. Subjects that Mirrors experiment with tend to end up dead very fast - they're often discovered by doing things like projecting human hands onto birds or frogs.
Once trained, though, Mirrors are incredibly powerful healers. If they can properly isolate the areas they want to replace, they can perform surgeries without cutting the other person open at all (not recommended, opening them is safer) and replace lost limbs.
Mirrors have several limitations. First and foremost, you have to have the part you're replacing. For instance, if a Mirror is born without a right arm, they would not be able to heal someone else's right arm until their own was replaced by another Mirror. Second, when the replacement is done, the replica matches the Mirror's exactly. If a blue-eyed Mirror replaces the eye of a brown-eyed person, their new eye will be blue. Replacing skin to cover surface wounds will leave the other person with a patch of skin matching the Mirror's. If a thin, delicate man loses a leg and the only Mirror available is a burly man a foot taller than him, replacing the leg will result in a mismatch of height so egregious the person probably wouldn't be able to walk anyway.
As a general rule, Mirrors who have not had years and years of anatomical study tend to stick to surface damage. Being able to see exactly what area you need to replace makes mirroring much easier. Temples that offer anatomical study also tend to collect Mirrors of as wide a range as possible, even going so far as to trade Mirrors with sister temples to have better coverage. While low class populations are generally happy to get the attention of almost any Mirror, nobles and the wealthy see mismatching skin/hair/eyes/etc to be gross and they invest only in the services of Mirrors as close to themselves as possible.