A Magic character's color alignment doesn't imply a moral judgment on them. Every color of Magic has more or less equal capacity for good and evil - the difference is in what values each of their outlooks emphasize, and what virtues and flaws they each have. Now, since just about every trait can be assigned to one or more colors (that's the point of Magic's color philosophies, after all), saying a color does evil in certain ways and good in others is a gross generalization. Still, in order to bust the conception that certain colors are good and certain ones are evil, I'm starting a series to go through the good and evil traits of each color in Magic, starting with the first one in WUBRG order - white.
White's good qualities: The classic high-fantasy hero is white. The color cares about justice and order (or what it sees as these concepts), and is most likely among the colors to have a personal code of honor. White is the Knight in Shining Armor - high-minded, self-serious, and incorruptible. White is idealistic (perhaps to a fault) and is willing to give up much of its own self for a higher cause. White cares about religion and keeping itself pure and holy. White believes healing is a worthy calling, and often prefers peace to war no matter the circumstances; white is the most likely color to be pacifistic. White thinks it's right to go out of your way to defend the weak. White thinks that lawbreaking and troublemaking should be duly punished and prevented in the future. In George R.R. Martin's "A Song of Ice and Fire" series, Ser Barristan says this, which demonstrates what a good white-aligned character is like:
"It is chivalry which makes a true knight, not a sword … without honor, a knight is no more than a common killer. It is better to die with honor than to live without it."
White's evil qualities: White thinks it knows what's best for everyone. This can lead to it being quite helpful, but often indeed meddlesome, and sometimes tyrannical. White's sense of morality allows for no gray areas. White can be self-righteous, and prone to religious delusions. If a person's mental illness manifests as them hearing the voice of God, that is a white kind of disorder. A white character who thinks themselves divinely elected will take this as license to do whatever they feel is necessary. C.S. Lewis wrote this about a type of evil that under Magic color philosophies would be considered white-aligned:
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience. They may be more likely to go to Heaven yet at the same time likelier to make a Hell of earth. This very kindness stings with intolerable insult."