Drop down list does not work same as type

Hello,
I am tring to write a code to change color of cell when cell values matches perticular value.
Attached is the test file.
When cell value of B1 becomes "1" color changes to red.
The code works well if I type in cell B1.
When I use drop down list (Data/Validation/List) it doesn't work.

PLease help me.

Regards,
SWapnil