Add systemPreferences.getColor specs

spec/api-system-preferences-spec.js

@@ -15,6 +15,22 @@ describe('systemPreferences module', function () {
     })
   })
 
+  describe('systemPreferences.getColor(id)', function () {
+    if (process.platform !== 'win32') {
+      return
+    }
+
+    it('throws an error when the id is invalid', function () {
+      assert.throws(function () {
+        systemPreferences.getColor('not-a-color')
+      }, /Unknown color: not-a-color/)
+    })
+
+    it('returns a hex RGB color string', function () {
+      assert.equal(/^#[0-9A-F]{6}$/i.test(systemPreferences.getColor('window')), true)
+    })
+  })
+
   describe('systemPreferences.getUserDefault(key, type)', function () {
     if (process.platform !== 'darwin') {
       return