Autohotkey-Gui-Edit : Can section and key be read in different color in ini file?

The control type GUI Edit is an area where free-form text can be entered. It does not do highlighting to display elements in colors.

You need to parse the text yourself and create the highlights yourself.

To help with the task, you may convert the text into HTML, perhaps using Regular Expressions, and display it using the library HTMLText.

An example given in the documentation for how the colored text is to be created is:

<fGeorgia><w100>Light text in Georgia</w></f><w1000>Heaviest text</w>Normal Text<u><i><b>This is underlined, italic and bold </b></i></u><cff0000><d>This is red and Deleted</d></c>