Sandblasted steel, depending upon the existing surface rust and mill scale, as well as the type of abrasive used for sandblasting, will give a different appearance, even when following the same specifications.  This has been a caused of concern when sandblasted work may not “appear” to be completed to specification, but may actually be “complete as specified”.  This Sandblast Color Chart will hopefully help to determine when sandblasted surfaces meet specifications.  Keep in mind, coloration (or hue) on any metal will be determined by both the type of rust (if any remains) and also the aggregate used during sandblasting operations.