bbwincmd.exe [xymon server] status+2m [hostname] alive green "Last signal received at %time% on %date%"

This does send a green status every minute, but when I manually stop the script from being executed, the status becomes grey instead of purple.

It should go purple, unless you have the host configured with the "dialup" keyword in hosts.cfg, or if you are ping'ing it and the "conn" status is red. If the latter case, then you can add "noclear" in hosts.cfg:

    noclear
           Controls whether stale status messages go purple or clear 

when a host is down. Normally, when a host is down the client
statuses ("cpu", "disk", "memory" etc) will stop updating - this would usually make them go "purple" which can trigger alerts. To avoid that, Xymon checks if the "conn" test has failed, and if that is true then the other tests will go "clear" instead of
purple so you only get alerts for the "conn" test. If you do want the stale statuses to go purple, you can use the "noclear"
tag to override this behaviour.

Regards, Henrik