Grow woad, extract the blue pigment, dye your own wool with woad indigo, and knit a blue scarf to wear when you next climb a mountain (or do something less energetic...)!
Learn more about the Woad plant (Isatis tinctoria), a famous source of natural indigo dye and how it has been used for several thousand years (see woad history) in Europe and the Middle East. Woad dye extraction produces natural indigo dye from the dark blue-green, spinach-like woad leaves.