Answer by Ray for How to fall back to the default Color Theme in Emacs?

Try:

M-x color-theme-select

Move point (the cursor) to first line showing:

[Reset]

and press 'Enter' (return).

Alternatively, to get back to the Emacs default themes, also try:

M-x color-theme-emacs-21

or

M-x color-theme-standard

However, from your question it's not clear which theme you initially started with. For example, if you simply been using the default theme provided in the color-theme quickstart when you first (manually) installed color-theme then do this:

M-x color-theme-hober

or whatever you had specified in your .emacs file (if applicable).