Bug in gradient background

Very new to ParaView {about 3 days}. Running a recent version (5.6.0 64-bit, Qt Version 5.9.5) under Ubuntu Linux v 18.0.4 for OpenFoam data. Trying to create a gradient screen background. I open the “Paint Palette” thingy at the top and go to "Edit Current Palette". It lets me select the two gradient colors. Gradient color #1 works {as you can see I set it to grey}, but Gradient color #2 Never works. It always remains very dark blue or black. As you can see here I set it to light green (and clicked Apply) but it remains dk blue or black.

Posted this under the Paraview forums and somone replied back that "it's a bug". So posting here.