Yes, it is.
We just recommend that you don't call "your" template as "classic" or "template_default". Almost any other name will suffice.
One of the main reasons for this is so that if we make an update to the supplied "classic" template files in the next version, and you mistakenly assume that you can just upload all the new files in order to upgrade, then you'll wipe out your customizations and won't be very happy.
Upgrades will still require merging changes into your customized files, but if your customized template goes by a different name, it's faster to isolate potential issues.
A second big reason for keeping it separate is so that you can easily switch "back to classic" in order to peek at the way your site looks if it was based on defaults. That way if a customization change you made caused something to be busted, you could quickly switch back and see if it was also busted in Classic. Then you'd know whether a change you made was related to a templating issue or some other part of the code.
So ... at present, you could rename your "classic" folder to "justmine" or something, and edit the template_info.php file inside the folder to reflect the name. Then if you've used any other "classic" folders on your site, you could rename those as well. After doing so, I suggest you re-upload the original "classic" folders so you have something available to "switch to" if you need to test against the default layout.
As for the "soft colors" that you didn't like so much ... those were just from the template_default stylesheet. They're set that way so that you "do" change them and so that they're easier to locate specific parts to change to your liking. Some people can't see past the colors and think they're in a paint factory that just had an accident. It's not really that bad :) ... just identify the color and change it to what you desire.




