I am trying to set active colour to "BYLAYER" with Lisp

Have tried:

(setvar "SETACTLCLR" "256")

(setvar "SETACTLCLR" "ByLayer")

Neither work, but works for all other options including (setvar "SETACTLCLR" "0") for ByBlock

(command "SETVARIABLE" "SETACTLCLR" "256") also does not seem to work