src/vs/platform/theme/common/colorRegistry.ts/ColorRegistry/deregisterColor
class ColorRegistry:	public deregisterColor(id: string): void {
		delete this.colorsById[id];
		delete this.colorSchema.properties[id];
		const index = this.colorReferenceSchema.enum.indexOf(id);
		if (index !== -1) {
			this.colorReferenceSchema.enum.splice(index, 1);
			this.colorReferenceSchema.enumDescriptions.splice(index, 1);
		}
		this._onDidChangeSchema.fire();
	}