Inside of Member App there is a wide selection of different themes that you can select for your Membership.
Toggle 'Default' in the settings type switch to choose default settings.
Select the your base theme from the dropdown. The list of your available themes may vary.
Select your theme color preset from the 'Select theme colors' dropdown.
Toggle 'Default' in the settings type switch to choose advanced settings.
This will allow you to customize your font by selecting a different one from the list of available fonts in 'Chose a font' dropdown.
Next select background, sidebar, main color, second color and text color by clicking on the color and using a color picker or inputting a new color as hex.
Click 'Next' to save your changes.