I do not know is it possible or not. I have a content type for creating tickets. I have a form attached to content type which contains ticket state and ticket assignee fields as drop down. Now I want to create a Rule when state of ticket updated then send an email to ticket creater. The problem is that I could not find the state field values as token.
If I understand your question correctly you want send email after state field changes by Rule:
Create a new rule that will react to the After updating existing content event
Use the following condition:
Data comparison: node:field-your-field(maybe field-state) and node-unchanged:field-your-field
Select Negate: FALSE
Create the action
Send the email