Friday was the quietest and most uneventful day of Astros spring training since manager Bo Porter began his season-long overhaul. Except for four minutes. Six weeks after being suspended from baseball because of his second failed drug test, Astros first-base prospect Jonathan Singleton addressed the media at Osceola County Stadium. Singleton spoke quietly and sometimes failed to make eye contact, employing brief answers and often resorting to clichés. But he responded to every question that was fired his way, insisting he will show his “true colors” moving forward. Singleton, 21, has yet to play above the Class AA level. But in another sign of the depth of the Astros’ massive rebuild, the organization is counting on the lefthanded slugger to deliver on major league potential that resulted in him recently being named the club’s No. 2 overall prospect by Baseball America. “I believe this is an opportunity for me to leave the past behind and move forward,” said Singleton, who was suspended 50 games Jan. 9 for failing a minor league drug test because of marijuana use. “I’m an honest, up-front guy, so you’ll see who I am in the coming future.”