Hi Jeff
I approved your post earlier but I'm having difficulty in replicating the issue you described in either Access 2016 (365) or 2010
I tried several things including:
a) copying a form
b) copying controls from one form to another
c) dragging a form from one open Access app to another
d) importing a form from another Access app
Each Access app can only have one theme. If you don't set a theme it uses the default Office Theme.
In a) & b) the theme is applied to the new form as that is built into the app
In c) & d), the imported form will take on the theme of the destination app so if that has a different theme, the form will indeed change appearance if it was based on theme colours from the top half of the colour picker e.g. Accent1, Text1 etc.
However if you you customise the form colours/appearance in the original app so its using standard colours rather than theme colours, its appearance will be retained when it is imported to a new app
Please could you clarify the situation that has caused you problems requiring a solution such as this