How do I change the color of my lightning icon?

Icons are created with no background color. The base .slds-icon class sets the fill color to white. You can change the color by changing the CSS fill property value. Use the .slds-icon-text-default class to make a utility icon the same color as the default text. .slds-icon-text-warning creates a yellow warning icon and .slds-icon-text-error can be used to make a red icon.