Unfortunately you may not do it with WindowBlinds. However there is one hard way to recolour this areas manually through editing ieframe.dll file. I've done this a few times but, it seems to me, this way will not be popular...
1. You need use ResourceTuner to extract and edit (replace) some bitmaps: 308.bmp, 514.bmp, 515.bmp, 516.bmp, 517.bmp, 571.bmp, 572.bmp, 576.bmp, 577.bmp, 578.bmp, 582.bmp, 626.bmp, 627.bmp, 628.bmp, 629.bmp, 630.bmp, 654.bmp, 656.bmp and 769.bmp - IE toolbar backgroung. As well as the XML-resources (20481.xml, 20737.xml, 20739.xml, 20740.xml) - gradient of IE tabs.
2. Besides you need any Hex Editor and RGB to HEX converter to edit the gradient color of IE sidebar:
2.a key: 0x00B8 color: 0xE3EEFB - top area
2.b key: 0x00B9 color: 0xF1EDED - bottom area.
3. And finally you need enough free time to make these hacks.
Don't forget to create the untouched copy of ieframe.dll before you begin (if you are really ready)!