The "Add Text" tool (Tools>Edit PDF>Add Text) is not the same as the typewriter tool in Acrobat X. It's the same tool as the Tools>Edit Text&Obects>Edit Document Text while holding down the Ctrl or Option key. It will create static PDF text, whereas the typewriter tool created a text annotation. You can do that by selecting Tools>Comment>Text. This will allow you to save the settings you applied to one text annotation as the default for all text annotations you create from now on. To do that, select the annotation in the list of annotations and right-click on it, then select "Properties" from the menu:

On the dialog that pops up, select to make the current properties the default:

When you now create new text annotations, they will use the color and font/font size that you specified as the default.