Do I have to use IMCE?
No. Acquia Cohesion allows the site builder to select, either use of IMCE or Entity browser for browsing and selecting images.
Acquia Cohesion renames to Site Studio from version 6.2. Tell me more.
Color tags allow you to create groupings of colors based off of the color tags that you define in the website settings color palette.
Yes, you can use Drupal fields in certain parts of Acquia Cohesion.
It depends on the use case. For fields and their field formatters use a 'Field' element, for data without field formatters, use a token.