We do not manufacture this product in grey/concrete color, however we have developed a paint color specifically for this purpose, which can be found at any local Home Depot. For more information on how to get this color, please email us at curbramp.us@gmail.com with your order number.
Regarding the painting process, you will need to apply a light primer to assist with adhesion, then simply paint it on with a brush. Please refer to the attached sample images to visualize how this product looks when painted.