Well, it's easier than you think and does not require any work. Here are 3 options off the top of my head:
A. First, some background. The User/Programming Guides are CHM files, or "compiled HTML help" files, which in turn are rendered by Internet Explorer. Since 1990s, IE has always had such accessibility options as override colors and fonts on web pages, apply a custom CSS etc. Your job is to leverage this ability by following
this guide which boils down to 3 ultra easy steps:
1. Open up Control Panel > Internet Options.
2. From the General tab, click Colors.
3. Uncheck "Use Windows colors" and then select the colors you want to use. You need to override the Background color to the one of you liking. Voila.
As Internet Explorer is rooted deeply into the system, the option "A" is a system-wide change.
Countless applications rely on IE engine to render HTML content, so all they are going to be affected by this change, even though you can revert it with a couple of mouse clicks. If it scares you, or reconfiguring IE options before viewing WLP Help and reverting the change back seems uncomfortable, here are 2 alternatives:
B. Just use a 3rd party CHM viewer that allows to change background color, to open the CHM files that reside in Wealth-Lab's main folder (WLNetUserGuide.chm and WealthScriptGuide.chm), for example:
CHM ViewerSumatra PDFC. To think of it, you can just change the background color in the Guides if you download their PDF versions from Fidelity's website. Almost any PDF viewer these days, be it Adobe's (which I strongly do NOT recommend), Foxit, SumatraPDF, or whatever, has an option to set custom background color.
P.S. I believe that my instructions are enough for anyone to easily apply, so I appreciate if no support questions on this matter will follow. I've showed you
three workarounds but supporting any 3rd party software is not covered by our license agreement. As always, the internet is an endless resource if one searches good enough.