diff --git a/packages/utils/src/ColorUtils.js b/packages/utils/src/ColorUtils.js
deleted file mode 100644
index 94124f4d49..0000000000
--- a/packages/utils/src/ColorUtils.js
+++ /dev/null
@@ -1,29 +0,0 @@
-class ColorUtils {
-  /**
-   * Checks if a background color is dark (i.e. should use a light foreground).
-   *
-   * @param {string} background the background color
-   */
-  static isDark(background) {
-    const d = document.createElement('div');
-    d.style.display = 'none';
-    d.style.color = background;
-    const color = getComputedStyle(document.body.appendChild(d))
-      .color.match(/\d+/g)
-      .map(a => parseInt(a, 10));
-    document.body.removeChild(d);
-    const brightness = ColorUtils.getBrightness(color);
-    return brightness < 125;
-  }
-
-  static getBrightness(color) {
-    // http://www.w3.org/TR/AERT#color-contrast
-    return Math.round(
-      (parseInt(color[0], 10) * 299 +
-        parseInt(color[1], 10) * 587 +
-        parseInt(color[2], 10) * 114) /
-        1000
-    );
-  }
-}
-export default ColorUtils;
diff --git a/packages/utils/src/ColorUtils.ts b/packages/utils/src/ColorUtils.ts
new file mode 100644
index 0000000000..51ba6d61b1
--- /dev/null
+++ b/packages/utils/src/ColorUtils.ts
@@ -0,0 +1,34 @@
+class ColorUtils {
+  /**
+   * Checks if a background color is dark (i.e. should use a light foreground).
+   *
+   * @param {string} background the background color
+   */
+  static isDark(background: string): boolean {
+    const d = document.createElement('div');
+    d.style.display = 'none';
+    d.style.color = background;
+
+    const computedColor = getComputedStyle(document.body.appendChild(d)).color;
+    const colorTokens = computedColor.match(/\d+/g);
+    let color: number[] = [];
+
+    if (colorTokens) {
+      color = colorTokens.map(a => parseInt(a, 10));
+    } else {
+      throw new Error(`Invalid color received. Got ${computedColor}`);
+    }
+    document.body.removeChild(d);
+    const brightness = ColorUtils.getBrightness(color);
+    return brightness < 125;
+  }
+
+  // Note: leaving this as arbitrary length number[] in case of RGBA().
+  static getBrightness(color: number[]): number {
+    // http://www.w3.org/TR/AERT#color-contrast
+    return Math.round(
+      (color[0] * 299 + color[1] * 587 + color[2] * 114) / 1000
+    );
+  }
+}
+export default ColorUtils;