on WordPress Updates Blog:

We’re happy to announce new improvements to your WordPress.com dashboard for a more accessible and customized experience. From your desktop, you can now customize your dashboard by choosing one of our two new color schemes, Classic Bright for a fresh modern feel and Classic Blue as the standard you’ve known and loved. As part of our commitment to inclusive design, these new colors have been optimized for higher contrast and increased legibility. We’ll soon be introducing additional color scheme options that will continue our mission of a better more accessible web for everyone.

How to customize your color scheme

FREE THEME WORDPRESS USERS PLEASE NOTE:

Go to PLANS – BILLING HISTORY – ACCOUNT SETTINGS if you want to change from the new Classic Bright default, back to original Classic Blue.