Hi Ancuta Me,
There is a workaround for your problem and it will work exactly how you would like it to work ... So i suggest that you try to do it as follows:
1- Go to Modules, Generic content then create a generic content and add your html there (let's say you call it GreenBox)
2- On each template you will drop a generic content wherever you would like then you would select this generic content that you created earlier using the "Select Shared Content" in the generic content editor under the RadEditor ... and use the GreenBox that you created
Thus you can edit your Green Box from one place (the modules -> Generic content) but you would use it on all of your templates.