How to use:
--- Open 'Glass Mug Mockup.psd' in Photoshop CS6 or newer
--- Double click on the red labelled [YOUR DESIGN HERE] layer thumbnail
--- Replace the placeholder design with your own design
--- Save and close the Smart Object
--- Show the the green labelled [CONTENTS COLOR] layer thumbnail
--- Double click on the layer thumbnail and use the color picker to choose a custom color
--- Double click the [BACKGROUND COLOR] layer thumbnail to also choose a new background color