I can't find a high contrast theme via "Customise look and feel".
This is something similar to the high contrast theme in MS Windows.
Lubuntu does not include a high contrast theme by default. But you can install one yourself by running sudo apt-get install gnome-accessibility-themes
from your terminal. Once the software is installed, you can open Customize Look and Feel
to switch to that theme.
There are three aspects: widget, icon, and window border. Unfortunately, the window border aspect isn't covered by the gnome-accessibility-themes
package. However, the default window manager in Lubuntu, Openbox, is highly customizable and most of the visual aspects can be altered by editing a plain text file, .themerc
located here: /usr/share/themes/openbox_theme_name/openbox-3/
. If you need specific help with that you could always ask :)
Alternatively, you could look at various sites that offer window border themes. Box-look.org is one such site. And High Contrast BlackandWhite maybe of interest to you.
This Lubuntu page has a bit about accessibility concerns.