forms: How should you change the normal text in black to show that it has become editable?

I am creating an application to use on Android phones. The main purpose of the application is to display information, in the format of a form, to the user. The user must manually fill in several fields of the form, but after the first time it should be rare to change them.

For example, the user must specify their email address. It is unlikely that the user will change their email address, but I still want to give them the option.

Right now I have a button that the user can press to allow edits, and then you can press the same button to save the changes. The text is normally black, but when it is editable it turns blue.

Does it exist anyway can it be clearer that the text is editable? I tried the gray, but then with a clear color it was difficult to read the text. Blue is fine, but it looks like a hyperlink and people do not usually associate blue with being editable. I also want the editable text to be easy to read, so that people can see what they are writing and because it is only necessary to make a slight adjustment.

I was also thinking of having a separate screen where the user can enter their information, but this seems a waste, since the separate screen would look exactly like the main screen (except without the information that is generated automatically).

Here is a fictional example to help illustrate what I am talking about. When the "edit text" button is pressed, some of the items in the column on the right can be edited, such as the phone number (but not the date it was automatically completed). How can it be shown in the user interface that the fields can now be edited?