Visual CSS tools with live previews: gradients and shadows you design by eye and copy as code, color conversion between HEX, RGB and HSL, a contrast checker with real WCAG verdicts, and a color picker that reads exact pixels from any image.
The Contrast Checker earns special mention: 4.5:1 for normal text is the accessibility bar audits actually measure, and checking takes ten seconds here.
All of these produce CSS rather than image files, which matters more than it sounds. A gradient or a shadow written as CSS scales to any size, adapts to a theme change, costs no extra request and stays sharp on every display, where the exported PNG equivalent does none of those things. Design it here against a live preview, copy the declaration, and paste it into your own stylesheet: there is nothing to sign up for and nothing to link back to.