JR,
Yes, I agree that the axis.tcl file is hard to follow. I started out my revamp just like you, with absolutely zero knowledge of TCL. I spent the majority of my time commenting out the code and cleaning it up, making it easier to manipulate.
Most of the elements do not have attributes and use the default values assigned by TCL, and have to be added in order to change their appearance. My example elements may not be named exactly the same, but it should give you an idea.
Here is an example with attributes:
frame .gcodepanel.readout
-borderwidth 0
-highlightthickness 1
-highlightcolor "#000000"
-highlightbackground "#000000"
Using the search function in gedit is very helpful in determining how all the elements are linked together.
Here is an example of a restyled button:
Button .controls.toolbar.estop
-activebackground "#ff0000"
-background "#ff0000"
-helptext [_ "Toggle Emergency Stop [F1]"]
-borderwidth 5
-font "Helvetica 12"
-height 2
-width 6
-highlightthickness 1
-highlightcolor "#000000"
-highlightbackground "#000000"
-takefocus 0
-padx 5
-pady 5
Remember, my element names will not be the same as the original axis.tcl code.
For some reason the forum is not allowing backslashing in the code sections. Each attribute line break must end with a backslash.