To help Google Forms users create more personalized surveys, feedback forms, quizzes, and more, Google is introducing new theme customization options. Specifically, you can now choose colors and fonts to theme your form.
Pick a theme and background color
You can choose a color for your theme. When you choose a theme color, it will apply to your header background, titles, action buttons, and more. You can pick a predefined color, or a custom one. After you pick a theme color, you can select a complementary color for the background.
Use an image for the form header
By default, the form header matches the theme color you select. If you want, you can change this and use an image to display in the header instead.
Customize the font style
You can pick from several font styles to apply to your form. When you pick a style, it will apply to your form title and question text.
Source: G Suite Updates