By default, a string indicator blinks in red when it is set to blink in the property node. i would like to know if is it possible to change this color??
You can't, but here's an article about how you can fake it if you really, really need something like that.
Actually, you can change this, but the change is global. The details are at the bottom of the article billko linked to.
Note that this is set in the INI file, so if you're building an EXE you will have to find the relevant line in the LabVIEW.ini file and put it in your EXEs INI file.