Running "watch" task
  Waiting...
  >> File "../scss/theme/_color-mixins.scss" changed. <br />
  Loading "sass.js" tasks...ERROR
  >> Error: `libsass` bindings not found in /Users/~path/_build/node_modules/grunt-sass/node_modules/node-sass/vendor/darwin-x64-47/binding.node.
   Try reinstalling `node-sass`?
  Warning: Task "sass" not found. Use --force to continue.
  • Step 1: run npm update from the grunt directory with your package.json. This should fetch the latest dependencies that are specified in your package.json file.
  • Step 2: Likely if you try to run grunt, you'll experience a binding error that reads as follows:
    Node Sass could not find a binding for your current environment: OS X 64-bit with Node.js 4.x. Usually this error is followed by the suggestion to of using rebuild node sass.
    Run npm rebuild node-sass
  • Step 3: If you're still receiving sass build issues: try updating grunt
    npm install -g grunt-cli and re-running the above. Also you may need to update Node itself and check your package.json versioning.