Where to find or how to make large harmonious color palettes?

For a website, I have a list of some 500-1000 items. I would like to display them individually with(in) e.g. a colored card but also as combinations of 2 up to ~5 items/colors. So, if I would display a rose, it would be a red card; if a daffodil, it would be a yellow card. Together, it would make a card where I display red and yellow.