Colour contrast between text and background is important on web pages. It affects some people’s ability to perceive the information (in other words to be able to receive the information visually).
Jakob Nielsen's 10 general principles for interaction design. They are called "heuristics" because they are broad rules of thumb and not specific usability guidelines.
SVG graphics can be animated using animation elements. A lot of very impressive effects can be created, especially ones involving morphing and transforming shapes. The sky’s the limit.
SVG
A Guide to SVG Animations (SMIL)
Knowledge
100 Tools to Launch & Grow Your Start-up Without Web Weveloper, Graphic Designer and (almost) Without Money