I don't like the new "tags".
I'd like to be able to colorize some Finder icons.
Preview allows me to "adjust the color" of icons, but only between Purple and Green.
Is there a simple way to add other colors?
If you mean to change the actual icon that represents the folders (i.e. double-click on it to open the folder), then there's a good, short article at http://www.visualpharm.com/articles/change_mac_icons.html that explains how to do this if you have icons you would already like to use.
In a nutshell, you right-click (control-click) on the Documents folder and choose "Get Info" from the menu that pops up. Then, choose an icon you'd like to replace it with.* Double-click it to open it in Preview, select all by pressing command-a, and then copy it by pressing command-c. Click on the icon of the Documents folder at the top of the Info window and paste the copied icon into its place using command-v. To remove the custom icon, select the icon you pasted in the Info window and press the delete key to restore it to its original icon.
As for colorizing icons, there are numerous applications that allow you to edit images. Pixelmator is a good one, relatively inexpensive as far as image editors go, and has a colorize option, as well as Adobe's Photoshop. There are also free alternatives that can be found with a bit of web searching.
*You can create the icon from the one already there by selecting it in the Info window, pressing command-c to copy it, and opening up a blank document in your favorite image editor and pasting it into it. From there, you can edit it any way you like, then save it as a .png to use it as an icon.
If you mean the color-coded bars that would highlight the text, called labels, those have unfortunately been retired in Mavericks in replace of tags. Hope this helps solve your problem.