diff --git a/types/d3-color/index.d.ts b/types/d3-color/index.d.ts
index 931ac29b96..56812a6bdb 100644
--- a/types/d3-color/index.d.ts
+++ b/types/d3-color/index.d.ts
@@ -32,7 +32,7 @@ export interface ColorCommonInstance {
      * Returns a hexadecimal string representing this color.
      * If this color is not displayable, a suitable displayable color is returned instead. For example, RGB channel values greater than 255 are clamped to 255.
      */
-   hex(): string;
+    hex(): string;
 }
 
 export interface Color {
@@ -108,9 +108,7 @@ export interface LabColorFactory extends Function {
 /**
  * Constructs a new Lab color with the specified l value and a = b = 0.
  */
-export interface GrayColorFactory {
-    (l: number, opacity?: number): LabColor;
-}
+export type GrayColorFactory = (l: number, opacity?: number) => LabColor;
 
 export interface HCLColor extends Color {
     h: number;