This documentation is quite confusing.

[cage]

On Fri, Jul 26, 2019 at 08:58:20PM +0200, Tom Hassel wrote:

Hello!

> I've been getting into ltk, since I wanted to do some GUI programming
> again.

Very good! :)

[...]

>
> The working code looks like this. How do I change the color of the button?

Long story short: ltk uses, by default, a set of widget (called "ttk")
that  does not  support many  configuration option  that the  old ones
supported instead.

But this  is only  part of the  story actually, I  think this  link on
stack overflow (see the accepted reply) also could help you:

https://stackoverflow.com/questions/53504488/ltk-button-height-not-configurable

and  the  link  below  (also contained  in  the  aforementioned  page)
probably is going to solve your issue:

https://mailman.common-lisp.net/pipermail/ltk-user/2016-June/000625.html

to try to clarify a bit more i suggest you take a look at:

https://www.tcl.tk/man/tcl8.6/TkCmd/button.htm

as you can see when the old widgets  (i.e. non ttk) are used you get a
command option: "background".   The value can be set  via the function
"configure" as shown in:

http://www.peter-herth.de/ltk/ltkdoc/node13.html

by comparison see the new, (ttk) widget:

https://www.tcl.tk/man/tcl8.6/TkCmd/contents.htm

it does have the  same option anymore, it use a  theme system to drive
the widgets visuals.

To change  a background button  of a ttk  you should probably  write a
theme but for lack  of skills, i can not help  much about that, sorry!
^^;

Tangentially i suggest you to stick with the ttk widget set as it help
to achieve a consistent visual  appearance that improve usability, but
this is matter of personal opinion i guess.

Hope this help!

Bye!
C.