I just re-install windows 8.1 then I've installed Windows8.1-KB2939087-x64, Windows8.1-KB2975061-x64, Windows8.1-KB2919355-x64, Visual C++ Redistributable for Visual Studio 2015 and Google Chrome. At that point everything worked normally except that the monitor identified as #2 in the picture below displayed the full HD (1920x1080) improperly.
To fix that I downloaded the Graphics driver for my APU processor with graphics (AMD Fusion APU A4-5000 Quad-Core with AMD Radeon HD8330 Graphics). That's when the second display went haywire and displayed everything in grayscale (though now 1920x1080 takes the entire screen unlike before)
I've also tried to reset my monitor; nothing changes. Also when I boot to windows 10 the color is back again which means this comes from windows 8.1 somehow.