See the attached link for all the information (and then some) for TX titles -
Salvage titles will be designated on the title itself. You can check a VIN on the TXDOT website for the title history. That certainly doesn't mean that something was salvaged in another state and later titled in TX, but it is a start at least.
Titles issued before 2003 I think were green if they were salvage. Blue for a regular title. The new ones aren't differentiated by color as far as I know.