Generate a QR for a poster, a card, or a product label, with a foreground color you choose.
Every visual artefact you ship has a tool behind it. The tabs that do not need a design system: a drop-resize-compress loop before a hero lands, a QR for a poster, a swatch you picked off a screenshot. All of those happen in your browser, so the artefacts never leave the machine you are sitting at.
Yes, within the error-correction budget - a QR code carries redundant data, and a level that tolerates roughly a third of the symbol being obscured is the safe choice for a centre logo. Keep the logo small, keep the quiet zone around the code clear, and test the printed size with a real phone.
Work from the scanning distance rather than the print size: the code wants to be roughly a tenth of the distance you expect people to scan from, and larger again in poor light or at an angle. A code that fills a business card is invisible on a wall.
Yes, provided the contrast holds - dark marks on a light background scan reliably, and light marks on a dark background often do not. Two mid-tone brand colours that look distinct to you can collapse to the same brightness on a cheap camera.