The converter supports light and dark themes, toggled by the circle button in the title bar. In the light theme, the button shows a moon icon. Click it to switch to dark. In the dark theme, it shows a sun icon. Click it to switch back to light.
All C Tech products with theme support, including Earth Volumetric Studio and the C Tech License Manager, share the same theme configuration. Switching the theme in any of these applications will cause all others to match that theme on their next startup.