In this paper, we construct the general Darboux transformation on the Sasa-Satsuma equation and represent the iterated solutions in terms of the three-component Wronskian. From the once-iterated solution, we derive the breather as well as the single-and double-hump solitons. We also analyze three types of collisions: soliton-soliton, breather-breather and soliton-breather collisions. The surprising result is that the soliton-breather collision may exhibit the shape-changing phenomena, that is, one breather (or soliton) may change into a soliton (or breather) when interacting with another breather. Such novel collision phenomena may be applied in all-optical information processing, optical switching and routing of optical signals.