When did the US military stop wearing blue uniforms?

What year did the US military stop wearing blue uniforms? I know that the US was wearing blue uniforms since as early as the American Revolution and as late as the Spanish American War, I want to know why and when they stoped wearing blue uniforms (well i understand olive drab is a better camoflauge and that camoflauge wasn't as important back then when soldiers would line up with no intention of hiding to show honor and courage. But it seems pointless making the US uniform an Olive drab for WWI when most of the war fought in trenches when the enemy knew where the US soldiers were like 99% of the time)