the pigment
Bleaching skin is a chemical change because it involves a reaction with the skin's melanin pigment that alters its chemical structure to appear lighter in color.
A chameleon changing color is a physical change. This color change is due to specialized cells in the chameleon's skin called chromatophores, which expand or contract to reveal different pigments based on the chameleon's mood or environment.
Bruises are the consequence of a physical action.
An example of color change is when a substance turns a differen color from a reaction.
pH lipstick contains pigments that react to the acidity of your lips, causing them to change color. When the lipstick comes into contact with the pH level of your skin, it triggers a chemical reaction that alters the color of the lipstick. This allows the lipstick to adjust its shade based on the unique pH of your lips, creating a personalized color.
Sun tanning is a physical change. It involves the melanin in the skin being activated by exposure to UV radiation, causing the skin to darken in color. No new substances are created during the process.
These compounds are melanins.
A Chamelion changes it's skin color to show how it is feeling
If you go to the west of Falador, you will see an icon on the World Map which shows Makeover Mage (alternativley, you could just search for the Makeover Mage on the world map and press enter). For a small fee of 3k, she allows you to change your skin color and/or change your gender.
melanin
"sunburn" results from physical damage caused to your skin by overexposure to Ultraviolet emissions, usually from the sun but it can also come from a UV lamp. UV light affects damage to the DNA of your skin cells. In defense those cells will produce melanin, a chemical response to try to repair this damage, which also darkens the color of the skin ( a "sun tan").
Chameleons use their cell structure in their skin to change color. This does not mean that if you put a chameleon onto a red surface that it will change red in color. chameleons can only change a few different colours, mostly used dependant on the mood of the lizard. It does how ever try to blend in as much as possible. So to camouflage it's self it uses it's cells and chemical reactions in the skin to change the color in it's skin.