A DeviceGray color — a single intensity in the 0.0..1.0 range in a
well-formed PDF, where 0.0 is black and 1.0 is white; see "Component
range" in PdfElixide.Color for what a malformed one can hold.
Only annotation colors can take this shape; see PdfElixide.Color.
Summary
Types
@type t() :: %PdfElixide.Color.Gray{gray: float()}