To specify a byte value use hex (hexadecimal) constants.

Hex constants are specified by an X followed by a single-quoted string composed of an even number of alphanumeric characters.

For example, x'01FF' represents a varbyte(2) where the first byte is 1 and the second is 255 (which is FF in hex).

An alternative is to use a prefix of 0x. 0x01FF is the same as x'01FF'.