Contrast Grid
A palette is not accessible on its own, only a pairing is. This puts every color against every other and tells you which combinations you can actually put text in.
The palette
One per line. Hex, rgb(), hsl() or a color name.
Put a label after the color and it will be used in the headings.
Settings
Judge against
Show
Every pairing
text down the side, background across the top
The pairing you picked
Click any cell in the grid.