I tried the 'no color' option (RGBA -,-,-,-), and it didn't really work for me either.
However, in the color pallete there is an option which has an RBGA value of [0,0,0,0]. Try that? Or you could also select "more", select the "RGBA" tab and set the "Alpha" to 0. Technically anything that has an A value of 0 is completely transparent. It worked for me.