My bad, I was using: Tkx::ttk__button()
whereas your code used: Tkx::button()
Sigh. BTW: I am writing my very 1st Tkinter code, so your help is greatly appreciated.

The latter surely supports "-background".
However, I still cannot get the color to change.
So, I reduced your example to 2 buttons, code at bottom.

One confusion is "what replaces the 'i' in: Tkx::i:..."
as noted in your "I FIGURED IT OUT" response:

  Tkx::i::call(".b", "configure", "-background", "blue");

  "You just have to change the letter [I presume ::i::] to match the button."

  "Undefined subroutine &Tkx::button::call...:

  -command => sub { print "18L\n"; print "18L #2\n"; },

  -command => sub { print "18L\n"; Tkx::.b::call(".b", "configure", "-background", "blue"); },

  -command => sub { print "18L\n"; Tkx::button::call(".b", "configure", "-background", "blue"); },

  -command => sub { print "18L\n"; Tkx::".b"::call(".b", "configure", "-background", "blue"); },

    while executing

    invoked from within

    ("uplevel" body line 1)

    invoked from within

    (procedure "tk::ButtonUp" line 24)

    invoked from within

    (command bound to event)

use strict;
use warnings;
use Tkx;
my $mw = Tkx::widget->new(".");
  $mw->g_wm_title("Jobs Not Forecasted");
    Tkx::button(".b",
        -text => "18-Letters",
        -background => "red",
        -width => 11,
-command => sub { print "18L\n"; print "18L #2\n"; },  # OK
#  -command => sub { print "18L\n"; Tkx::.b::call(".b", "configure", "
+-background", "blue"); },    # BAD, runtime error
#  -command => sub { print "18L\n"; Tkx::button::call(".b", "configure
+", "-background", "blue"); },# BAD, runtime error
#  -command => sub { print "18L\n"; Tkx::".b"::call(".b", "configure",
+ "-background", "blue"); },  # BAD, syntax error
    );
    Tkx::pack(".b");
                    
    Tkx::button(".s",
        -text => "EXIT",
        -width => 11,
        -command => sub { Tkx::destroy("."); },
    );
    Tkx::pack(".s");
    Tkx::MainLoop();
[download]

I posted #4 and after some more experimenting got things to work. Just needed to c/p cowboy's code literally. In my defense, his comment
"You just have to change the letter to match the button."
mislead me... who would have thought there was a Tkx::i::... method (the "letter i") and most real code wouldn't have used ".b" as the widget id. What a waste of time. FTR, the following snipped works as reported.

...snip...
my $mw = Tkx::widget->new(".");
  $mw->g_wm_title("Jobs Not Forecasted");
    Tkx::button(".b",
        -text => "18-Letters",
        -background => "red",
        -width => 11,
    -command => sub { print "18L\n"; Tkx::i::call( ".b", "configure", 
+"-background", "blue" ); }
},
    );
    Tkx::pack(".b");
...snip...
[download]

Hi,

I'm not cowboy :)

The  Tkx::pack(".s");... syntax cowboy using is very cumbersome , if you're going to do that, might as well just write it in tcl with the "secret"  Tkx::eval('tcl source code here'); , its a tiny bit less cumbersome than Tkx::i::call, but you gotta learn Tcl syntax

Yes Tkx::pack... is the first syntax explained in Tkx::Tutorial (a tutorial which must not be skipped), but don't choose that syntax :)

Also if you insist on Tkx don't skip http://www.tkdocs.com/tutorial/onepage.html

$Tkx::TRACE = 64;
use Tkx;
...
## create button
my $b = $mw->new_ttk__button(
    -text => 'Hello, world',
    -command => sub { $mw->g_destroy; },
);
$b->g_pack;

## retrieve existing button by name (button created using Tkx::eval())
## my $b = Tkx::widget->new(".b");

## Tkx::i::call(".b", "configure", "-background", "blue");
## Tkx::eval(".b configure -background blue");
$b->configure( -background => "blue")
[download]

doc chain is usually http://docs.activestate.com/activeperl/5.22/lib/Tcl/tkkit.html ... http://docs.activestate.com/activetcl/8.5/tcl/TkCmd/ttk_button.htm .. http://docs.activestate.com/activetcl/8.5/tcl/TkCmd/options.htm#M-background, http://docs.activestate.com/activetcl/8.5/tcl/TkCmd/ttk_style.htm

My feelings on tkx Re: Is there a Tk to Tkx translator script? (Tk, Tcl::pTk)