Hello George, Thank you for fast answer! I read that article and there is some issue with that. if you can see at it, i'd really appreciate it. So the problem is that if i do it directly from Tumblr, it will also block it from Tumblr users. Here is the note right below that option "Allow this blog to appear in search results":
"This applies to searches on Tumblr as well as external search engines, like Google or Yahoo."

Also, if i do it from GWT, i'm very concerned to remove URLs with my subdomain because i afraid it will remove all my domain. For example, my domain is abc.com and the Tumblr blog is setup on tumblr.abc.com. So i afraid if i remove tumblr.abc.com from index, it will also remove my abc.com. Please let me know what you think.

Thank you!

Hi guys, I read your conversation. I have similar issue but my situation is slightly different. I'll really appreciate if you can help with this. So i have also a subdomain that i don't want to be indexed by Google. However, that subdomain is not in my control. I mean, i created subdomain on my hosting but it is pointing to my Tumblr blog. So i don't have access to its robot txt. So can anybody advise what can i do in this situation to noindex that subdomain?

Thanks