Lexmark C2425
From the control panel, navigate to:
Settings > Print > Quality > Toner Darkness
For non-touch-screen printer models, press to navigate through the settings.
Adjust the setting.
Apply the changes.
How to Adjust Fine Line Widths for Lexmark CX/CS42x_52x_62x, MC/C2xxx and XCxxxx
Change the display brightness to see printer icons and text more clearly.