Color specs

Everywhere you type a color (a Static layer's fixed color, a book's palette, preview --color), nfty takes a color spec: a prefix, a colon, and a value. The prefix is required. A missing or unknown prefix is an error, never a guess, because guessing between hex: and hsv: silently produces the wrong art.

Prefix	Value	Example
hex:	Exactly six hex digits, rrggbb. Case does not matter.	hex:d6249f
rgb:	Red, green, blue, 0 to 255 each.	rgb:214,36,159
hsl:	Hue 0 to 360, saturation and lightness 0 to 100.	hsl:322,72,49
hsv:	Hue 0 to 360, saturation and value 0 to 100.	hsv:322,83,84

All four above are the same color. nfty writes colors back as hex: (lower case), the one form that survives a round trip exactly.

What a colored layer takes from it

A Dynamic or Static layer is a gray value-map: lightness comes from the drawing. From a color spec it takes only the hue and saturation. That is why an 8-digit hex:rrggbbaa is refused: the alpha pair would be parsed and then discarded.

Errors

Typed	Error
d6249f	missing a prefix (hex:/rgb:/hsl:/hsv:)
#d6249f	missing a prefix
hue:200	unknown color prefix
hex:d6249	must be exactly 6 hex digits
hex:d6249fff	has 8 digits (rrggbbaa); use 6-digit rrggbb
rgb:10,20	expected 3 comma-separated values