You can change the font size of the text in myTaxExpress by clicking on the View menu at the top of the program window. Then select the "Make Font Smaller" or "Make Font Larger" option. After doing so, close myTaxExpress and then relaunch myTaxExpress. The font size will be changed depending on which option you selected previously.
To change the background color, go to the View menu again and select "Background Colour". You will be prompted to select a new background color.