Function xparse_rgb 

pub fn xparse_rgb(r: u8, g: u8, b: u8) -> String

Format 8-bit RGB channels as an XParseColor rgb:RRRR/GGGG/BBBB string.

Each channel is duplicated into 16-bit form (0x80 becomes 8080). The returned string is suitable for the color payloads accepted by this module.