In my opinion, this will become an all time classic: https://www.refactoringui.com/

Misc curated lists of visual design resources (depending on how interpret question aka no domain target (web, gaming, music, video, arts, robotics, etc)):

Courses to learn UI/UX Design :https://www.toools.design/learn-ui-ux-design

Design Resources for developers : https://github.com/bradtraversy/design-resources-for-develop...

Design Resources for Developers : https://github.com/manishparui/design-resources-for-develope...

Design Reosurces : https://github.com/reinaldosimoes/design-resources

Awesome Creative Coding : (beginner/intermediate) https://github.com/terkelg/awesome-creative-coding