Macro format_byte 

macro_rules! format_byte {
    (hex_only, $byte:expr $(,)? ) => { ... };
    (hex, $byte:expr $(,)? ) => { ... };
    (bin, $byte:expr $(,)? ) => { ... };
    ($byte:expr $(,)? ) => { ... };
}

colorfully formats a u8 as hex => binary => decimal (=> char (if ascii))