Yes i know that i can add new style class in css, but how to add new style class to Online Editor. One of way is creat custom tag, but i fink that it is not dificult to use it for me but for simple user i fink it is to difucult. So maybe it is simple way change text color.
Yes, you can add new styles for any of the existing tags in the OE. Look at the content.ini for examples. Then add your new options in content.ini.append.php for your siteaccess and admin siteaccess.
Once you do, you can right click on any element for which you have allow custom classes and select "Properties". From there you can set the class.
When you preview and publish the content, it will be published like this: <p class='yourcustomclassname"> (if you added a custom class called 'yourcustomclassname' to the <paragraph> tag in content.ini
If you want the color to show up in the OE, you have to add your class to the editor.css in the ezdhtml extension design folder.
The downside of this is that you cannot apply color to only one part of a tag element (i.e. a few words in the middle of a paragraph) unless you created a custom class for the the bold or italic tag which used css to make it not bold, but a color instead.