Each colourway contains six fabrics, all in one hue.  Each piece, moving from darkest to lightest, is have the intensity of the previous one.  All are low water immersion dyed so the effect is mottled, though from dye bath to dye bath this varies and some of the dye colour carries better and for longer so the colours become more even.  Turquoise is a good example of that.

The step from one fabric to the next is not great, sometimes you don't see it until you put the next one beside it.  Colour is relative, so what it is sitting next to and between can determine how you see it.

The fabric is a high quality pfd cotton and is lovely and firm yet still drapeable.  Perfect for patchwork.  Fabric should be colourfast, but test beforehand.