In the same way that I wouldn't ask an artist to design a software library, I don't expect myself to choose colors, layout, or design correctly. When shown choices from designers, I can tell which ones I like, and which ones work, and so on, but hacking graphic aesthetics is something that takes years to get good at, as any kind of hacking.

I would recommend that you hire a designer, or make friends with some designers who can help you with this.