Ran into an issue today where I wanted rspec to use color output regardless of whether or not the project had it set up in the .rspec or spec_helper.rb files.
A super simple way to do this is to update your .bash_profile and override the rspec command with the colour switch:
Add the following to .bash_profile and save:
alias rspec='rspec --colour'
Reload the file:
And you should be all set! Just run rspec as you normally would and the colour switch will be added automatically via the alias.