A theme also provides an amazing option for styling your default WordPress login screen; you can find the option inside:
Dashboard >> Appearance >> Customize >> WordPress Login Screen.
Custom Logo: Select a custom logo to replace the default WordPress logo.
Background Image: Select the image to set as the background image.
Login Screen Background Color: Select a color to set as a background color.
Login Form Background Color: Select a color to set as a background color for the login form.
Login Form Text Color: Select color to set for text in Login Form.
Login Form Button Color: Select color to set for button color in Login Form.
Custom CSS: If you need any custom CSS to apply on Login Screen, write it here.