The only problem I see is that the colouring sheets need to be adult pictures and not childlike images. It requires much more effort to find but they are available. Once you have a great range of images from masters to mandela's you will find the engagement increases as does the artistic creativity
The Benefits of Coloring-in for the Elderly
Once you have a great range of images from masters to mandela's you will find the engagement increases as does the artistic creativity