Modern day galaxies populate a bimodal distribution, in both morphology and color space. Their morphological and color properties are also inter-related, with lenticular and elliptical galaxies exhibiting red colors and spiral galaxies usually exhibiting blue colors. In color space, there is a genuine dearth of intermediate colored galaxies, suggesting that the transition a galaxy undergoes to transform must be rapid, and quenching galaxies, rare. Gas - its presence, absence, and mechanics - serves as the anchor of a galaxy’s transformation from blue to red. I will discuss the nature of gas in transitioning and transitioned galaxies through two lenses: (1) How a galaxy transition is able to impact the behavior of molecular gas, and (2) how new observations of molecular gas in quenching and quenched galaxies has recast our understanding of how they ultimately metamorphose from blue, star-forming spirals into red, quiescent ellipticals and lenticulars.
