src/vs/editor/common/config/editorOptions.ts/EditorRulers/constructor
class EditorRulers:	constructor() {
		const defaults: IRulerOption[] = [];
		const columnSchema: IJSONSchema = { type: 'number', description: nls.localize('rulers.size', "Number of monospace characters at which this editor ruler will render.") };
		super(
			EditorOption.rulers, 'rulers', defaults,
			{
				type: 'array',
				items: {
					anyOf: [
						columnSchema,
						{
							type: [
								'object'
							],
							properties: {
								column: columnSchema,
								color: {
									type: 'string',
									description: nls.localize('rulers.color', "Color of this editor ruler."),
									format: 'color-hex'
								}
							}
						}
					]
				},
				default: defaults,
				description: nls.localize('rulers', "Render vertical rulers after a certain number of monospace characters. Use multiple values for multiple rulers. No rulers are drawn if array is empty.")
			}
		);
	}