DAPI bound to DNA is maximally excited by ultraviolet (UV) light at 358 nm, and emits maximally in the blue range, at 461 nm

Propidium Iodide (PI) binds nucleic acids by intercalation in the bases. When bound to nucleic acid it has an excitation maxima ~535 nm and an emission maxima ~615 nm. On a flow cytometer PI is typically excited by 488 or 561 nm and can be detected in a 610/20 bandpass.