Everyone hangs their flowers upside down in bunches, and everyone is broadly right. The colour, though, is won or lost before the string comes out.
Pick at the moment a flower is just fully open, on a dry morning after the dew has gone. A bloom picked past its best fades to hay no matter what you do; one picked too tight simply closes forever.
Drying doesn’t preserve a flower. It preserves the moment you picked it.
Then: small bunches, a dark airy room, and three weeks of leaving them alone. Light is the thief — the prettiest drying rack by a sunny window will cost you every petal’s colour.