A 561 nm laser option is now available for new 561 nm laser-ready Gallios flow cytometers. The new laser option can aid researchers in analysis of a range of fluorescent proteins and excitement of PE/PE tandems. Good excitation is offered for red fluorescent proteins such as mCherry and DsRed. Yellow-green excitation provided at 561 nm can produce less autofluorescence in cells, increasing the signal-to-noise ratio for PE and DsRed detection. There is nearly no crossover contamination in the green detection channel, allowing simultaneous fluorescein or GFP detection without blocking optics. The new laser is externally coupled through an optical fiber and can be field installed on new Gallios 561 nm laser-ready analyzers.