KDE Plasma Themes

The KDE TechBase : http://techbase.kde.org/Welcome_to_KDE_TechBase

The KDE taskbar (panel) is a plasma object so its configuration is through the KDE plasma theme configuration - the Development/Tutorials/Plasma/Theme is tellling:

http://techbase.kde.org/Development/Tutorials/Plasma/Theme -> http://techbase.kde.org/Development/Tutorials/Plasma/Theme#Theme_Colors

Theme Colors

You can provide a plasma color scheme that will allow
text, selected backgrounds and other items to blend well with your
theme by supplying a colors file in your theme folder. See the colors
file in the default theme for an example.

If the colors file is
omitted, plasma will take on the current KDE system colors. Note:
Theme SVGs will not be colorized unless they contain the
'hint-apply-color-scheme' element.)

More can be found from the Development/Tutorials/Plasma/ThemeDetails

http://techbase.kde.org/Development/Tutorials/Plasma/ThemeDetails -> http://techbase.kde.org/Development/Tutorials/Plasma/ThemeDetails#Colors

From the KDE mailing list - [kde] settings for font colors

http://linux.derkeiler.com/Mailing-Lists/KDE/2010-03/msg00011.html

The desktop, aka plasma, has its own themes. However, in a couple
places, they seem to interact with the normal kde colors as well.
Well either that or the themes I run don't have a couple things set
too well. This can be bad if like me you have a strong "reverse
color scheme" (that is, light text on a dark background) preference,
as that's uncommon and the assumption would be dark text on a light
background.

Unfortunately, unlike kde, where most of the colors are set
specifically, with plasma one has to choose a theme -- altho
individual components (, general color scheme, panel background,
desktop widget background, analog clock, etc) can be set to
different themes if desired. Editing individual elements within a
component, however, requires editing the text-based config files
themselves, unfortunately...

KDE Brainstorm

http://forum.kde.org/viewforum.php?f=83

A wish: http://forum.kde.org/viewtopic.php?f=113&t=101989

I would

I would use the non-transparent panel.

Opaque panel

Background

http://techbase.kde.org/Development/Tutorials/Plasma/ThemeDetails#.22Opaque.22_folder

"Opaque" folder

In the folder share/apps/desktoptheme/opaque the same hierarchy can be
found: when compositing is disabled files in this folder are preferred
over the corresponding ones listed above...

But you could use the opaque plasma object with the compositing.

Another theme

The KDE System Settings > Workspace Appearance > Desktop Theme has the "Get New Themes". There are themes with the opaque panels - the Aya seems to be one of them.

Mixing theme components

KDE System Settings > Workspace Appearance > Desktop Theme -> Details tab. Pick the opaque panel from another plasma theme. Note the panel background is not working at here. Maybe this is working there.

How it should work - tested with the KDE 4.10.2 - Air (default) desktop theme with the opaque Air theme panel

KDE System Settings > Workspace Appearance > Desktop Theme -> Details tab; Panel Background: File=/usr/share/kde4/apps/desktoptheme/default/opaque/widgets/panel-background.svgz -> Apply

Now the selected theme with the customize opaque panel background should be copied to the ~/.kde/share/apps/desktoptheme/.customized/.

BUT this doesn't seem to work with the panel background. I tried this with the "Translucent Background" (for the other plasmoids) - it was working.

How to get the customized panel background to work
(working at here)

1) Set the plasma desktop theme off from the "Customized"

2) Copy panel-background.svgz from the ~/.kde/share/apps/desktoptheme/.customized/opaque/widgets/ to the ~/.kde/share/apps/desktoptheme/.customized/translucent/widgets/

3) Remove/clean the plasma theme cache from the /var/tmp/kdecache-[username] (same as ~/.kde/cache-[hostname]). The KDE is caching things like a mad - and using the information from the cache.

4) Log out - log in (or kill the plasma desktop and restart the plasma-desktop)

The panel background should be opaque - at here it is.

A PNG image as the panel background: http://forum.kde.org/viewtopic.php?f=113&t=101989 -> http://www.kubuntuforums.net/showthread.php?56120-Customize-plasma-desktop-theme