--- a/devtools/client/inspector/rules/test/head.js
+++ b/devtools/client/inspector/rules/test/head.js
@@ -212,34 +212,16 @@ var waitForSuccess = Task.async(function
       ok(false, "Failure: " + desc);
       break;
     }
     yield new Promise(r => setTimeout(r, 200));
   }
 });
 
 /**
- * Get the dataURL for the font family tooltip.
- *
- * @param {String} font
- *        The font family value.
- * @param {object} nodeFront
- *        The NodeActor that will used to retrieve the dataURL for the
- *        font family tooltip contents.
- */
-var getFontFamilyDataURL = Task.async(function* (font, nodeFront) {
-  let fillStyle = (Services.prefs.getCharPref("devtools.theme") === "light") ?
-      "black" : "white";
-
-  let {data} = yield nodeFront.getFontFamilyDataURL(font, fillStyle);
-  let dataURL = yield data.string();
-  return dataURL;
-});
-
-/**
  * Get the DOMNode for a css rule in the rule-view that corresponds to the given
  * selector
  *
  * @param {CssRuleView} view
  *        The instance of the rule-view panel
  * @param {String} selectorText
  *        The selector in the rule-view for which the rule
  *        object is wanted

--- a/devtools/client/inspector/shared/test/head.js
+++ b/devtools/client/inspector/shared/test/head.js
@@ -1,24 +1,24 @@
 /* vim: set ft=javascript ts=2 et sw=2 tw=80: */
 /* Any copyright is dedicated to the Public Domain.
  http://creativecommons.org/publicdomain/zero/1.0/ */
 /* eslint no-unused-vars: [2, {"vars": "local"}] */
 /* import-globals-from ../../test/head.js */
-
 "use strict";
 
 // Import the inspector's head.js first (which itself imports shared-head.js).
 Services.scriptloader.loadSubScript(
   "chrome://mochitests/content/browser/devtools/client/inspector/test/head.js",
   this);
 
 var {CssRuleView} = require("devtools/client/inspector/rules/rules");
 var {getInplaceEditorForSpan: inplaceEditor} =
   require("devtools/client/shared/inplace-editor");
+const {getColor: getThemeColor} = require("devtools/client/shared/theme");
 
 const TEST_URL_ROOT =
   "http://example.com/browser/devtools/client/inspector/shared/test/";
 const TEST_URL_ROOT_SSL =
   "https://example.com/browser/devtools/client/inspector/shared/test/";
 const ROOT_TEST_DIR = getRootDirectory(gTestPath);
 const FRAME_SCRIPT_URL = ROOT_TEST_DIR + "doc_frame_script.js";
 const _STRINGS = Services.strings.createBundle(
@@ -235,18 +235,17 @@ function waitForSuccess(validatorFn, nam
  *
  * @param {String} font
  *        The font family value.
  * @param {object} nodeFront
  *        The NodeActor that will used to retrieve the dataURL for the
  *        font family tooltip contents.
  */
 var getFontFamilyDataURL = Task.async(function* (font, nodeFront) {
-  let fillStyle = (Services.prefs.getCharPref("devtools.theme") === "light") ?
-      "black" : "white";
+  let fillStyle = getThemeColor("body-color");
 
   let {data} = yield nodeFront.getFontFamilyDataURL(font, fillStyle);
   let dataURL = yield data.string();
   return dataURL;
 });
 
 /* *********************************************
  * RULE-VIEW