objective c - How to make a "within window" transparent/blurry title bar using a custom base color in Yosemite? -

i've been playing around nsvisualeffectviews in yosemite , transparent titlebars wondering if it's possible have custom title bar, own base color (not gray), act apple's.
here's current nswindow:
achieved setting following code on custom nswindowcontroller:

self.window.stylemask = self.window.stylemask | nsfullsizecontentviewwindowmask; self.window.titlevisibility = nswindowtitlehidden; self.window.titlebarappearstransparent = yes; 

that blue color custom nsview that's painting rect particular color. content below nstableview.
so, goal have titlebar work like, let's say, maps instead of having "base" color gray color, "base" color blue 1 , when nstableview scrolls, content appears below title bar.

any ideas on how achieve this? thanks

have tried setting blue color transparency of, e.g., 0.75 in blue view, , nsvisualeffectviewunderneath it?