Sometimes the text for the frequency is displayed too large if display scaling is turned on.
You can change the color of the spectrum, there is a little pop-down menu at the bottom of the spectrum that says “Theme:” and it likely has “Jet” selected. Try each one, see what you like.
Changing the spectrum color is possible but it may be pretty difficult as it involves changing registry settings. I would not recommend it at this time. One day we may build a color picker for wfview, which would be pretty cool.
Display scaling is in your operating system control panel somewhere. I don’t know where as I do not use windows personally. It will make everything significantly smaller when you turn it off, so you might not ultimately want to do it.