This should get rid of the horrible default background.
adjust the background settings: transparency off, pixmap none
; then "save theme settings"
If you don't like the colours, you can change them with the -f(oreground) and -b(ackground) switches. Paste the above into a terminal and play with X11 colours. If you remove these 2 switches completely, Eterm will default to black and white. If there are still problems, post a screenshot.
Eterm -g 90x30-0-0 -f DarkOrchid4 -b LightYellow1 --font-fx none --buttonbar 0 --scrollbar 0 -T "Scan channel $apchan"