How to change dash transparency?

There is no way to manage the Dash transparency as yet, though you can change the blur. The Dash colour is affected by your wallpaper though, so you may need to change the wallpaper.

If you choose the "Static blur" option the the Dash blur is set the 1st time you use the Dash per session.

So if you open the Dash over an appropriate background then that's what you'll get for the rest of the session, what you then open the Dash over won't matter

For a short time in 11.10 the "No Blur"; option used to provide a dark,solid dash, that's fallen by the wayside & no blur is pretty much worthless

Can be adjusted in the unity plugin > experimental settings in ccsm

If ccsm, (compizconfig-settings-manager) is installed & you wish to go directly to the unity settings then

Alt+F2, type in about:config and hit Enter.

It can also be set from terminal, 0=no blur, 1=static blur, 2=active blur (the default

Open a terminal and type the below command

gconftool-2 -s -t integer /apps/compiz-1/plugins/unityshell/screen0/options/dash_blur_experimental 1