Galaxies grow through both internal and external processes. In about 10% ofnearby red galaxies with little star formation, gas and stars arecounter-rotating, demonstrating the importance of external gas acquisition inthese galaxies. However, systematic studies of such phenomena in blue,star-forming galaxies are rare, leaving uncertain the role of external gasacquisition in driving evolution of blue galaxies. Based on new measurementswith integral field spectroscopy of a large representative galaxy sample, wefind an appreciable fraction of counter-rotators among blue galaxies (9 out of489 galaxies). The central regions of blue counter-rotators show youngerstellar populations and more intense, ongoing star formation than their outerparts, indicating ongoing growth of the central regions. The result offersobservational evidence that the acquisition of external gas in blue galaxies ispossible; the interaction with pre-existing gas funnels the gas into nuclearregions (< 1 kpc) to form new stars.