Re-installing Emacs will not help fix any problem due to installing a theme (just like redoing the road won't fix your car).
The undesirable effects that might linger after disabling a theme only apply to the currently running Emacs session.
Those undesirable effects should be considered as bugs and reported to the theme's author. They ...
(Variable color-themes is a list of your color themes. A given color theme is a function.)
You can use command color-theme-analyze-defun to check whether a function definition (defun) at point defines a color theme. It's defined in color-theme.el.
Here is its doc string:
Once you have a color-theme printed, check for missing faces.
This is used by ...