The following video outlines how to assign colours to icons from within the BLINK Hub app:
Highlight the icon of the unit whose colour you wish to change and open its Unit Settings using the icon in the bottom right hand corner.
You will be given the option to set the colour manually, or can use the devices auto assigned colour by selecting 'AUTO'.
If you have created groups, you can use the Group Settings to change the colour of all units in that group. Learn more about groups here.