I have got red color colonies on TSA plate and it is gram negative.

It is positive in following reactions.
indole, hydrolysis, phenol red, catalese.

I don't have my Bergey's reference manual with me but Serratia marcescens is sometimes red pigmented, always gram-negative and rod shaped, capable of gelatin and casein hydrolysis and catalase positive.

You can find more information about it here http://microbewiki.kenyon.edu/index.php/…