Colour Change Charm

"...he wished he had not mixed up the incantations for Colour Change and Growth Charms, so that the rat he was supposed to be turning orange swelled shockingly and was the size of a badger before Harry could rectify his mistake."

- Harry mistakes the Growth Charm for this spell

The Colour Change Charm (Colovaria) is a charm that causes an object or animal to change its colour; a witch or wizard can use it to change the colour of their hair, for instance.

Prior to 1991
Harry Potter used this charm to change the wig of his teacher at St. Grogory's Primary School a vivid blue colour.

1991
"Sunshine, daisies, butter mellow, turn this stupid, fat rat yellow."

- Ron Weasley trying to perform a Colour-Change Charm.

When Ron Weasley was eleven years old, his brothers Fred and George convinced him to believe that a nonsense poem was this particular charm. The incantation was supposed to turn Ron's rat Scabbers yellow, but being a fake incantation, it caused no change whatsoever.

Later that year, Headmaster Albus Dumbledore used this charm to change the banners in the Great Hall at the End-of-Term Feast from the green and silver of Slytherin House to the crimson and gold of Gryffindor.

1996
During Harry Potter's Charms O.W.L. in 1996, he accidentally switched the incantations for this and the Growth Charm, so that instead of turning the rat orange it grew to the size of a badger before he could reverse his mistake.

1997
Harry Potter used this charm when he came of age to change the robes of the Chudley Cannons posters in Ron's bedroom to bright blue.

Etymology
The incantation for this charm comes from the English words colour (the visual perceptual property corresponding in humans to the categories called red, blue, yellow, green and others) and vary (to make or cause changes in the characteristics or attributes of; modify or alter).

Behind the scenes

 * As Harry Potter confused the Growth Charm with this spell, it is probable that the two incantations are similar.
 * It is possible that Harry Potter used this to turn his eyebrow yellow in Harry Potter and the Half-Blood Prince. However, the -fors suffix in the incantation Multicorfors seems to indicate that spell is a transfiguration, and Harry was practicing transfigurations that day. Therefore, it seems likely he used "Multicorfors".

Appearances

 * Harry Potter and the Philosopher's Stone
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Deathly Hallows
 * LEGO Harry Potter: Years 1-4
 * LEGO Harry Potter: Years 5-7