UInt8

UInt8 stores values from 0 through 255. Byte is an exact alias for it.

local red: UInt8 = 220
local green: Byte = 128
local brighter = red + 1

Unsigned integers do not support unary -. Arithmetic is checked, so adding 1 to 255 traps instead of wrapping to zero.

local value: Int = 200
local octet = UInt8(value)

The conversion traps if the source is negative or greater than 255.