Tailwind Palette is a tool which generates shades and tints for colour with its Tailwind config. The preview of shades and tints is structured in a way that you can test contrasting colored text on it. Plus it comes with "copy and paste" tailwind config JSON
Craftbase is an open source whiteboard tool where you can create wireframe design, diagrams and collaborate with your peers.
With real-time updates across all devices, you can collaborate with your peers in real-time just by sharing them the board link.