A system, comprising: a first radiant source characterized by a first average excitation wavelength; a second radiant source characterized by a second average excitation wavelength that is different than the first average excitation wavelength; a sample disposed to receive radiation from the radiant sources, the sample comprising: a first dye; a second dye; and a third dye; a detector configured to measure emissions from the sample; a first emission spectral element characterized by a first average emission wavelength; a second emission spectral element characterized by a second average emission wavelength that is different than the first average emission wavelength; at least one processor comprising at least one memory including instructions to: illuminate the sample with the first radiant source and, in response, measure emissions from the sample using the detector and the first emission spectral element and measure emissions from the sample using the detector and the second emission spectral element; illuminate the sample with the second radiant source and, in response, measure emissions from the sample using the detector and the second emission spectral element; wherein at least one of the dyes is an off-axis dye, an "off-axis dye" being a dye having a first maximum absorption or excitation wavelength that is an absolute maximum over an entire spectrum of the dye and having a second maximum absorption or excitation wavelengths that is a local maximum and is separated from the first maximum absorption or excitation wavelength by at least 60 nanometers; and wherein each radiant source is characterized by electromagnetic radiation within the visible light range, near infrared range, infrared range, or ultraviolet range. a first radiant source characterized by a first average excitation wavelength; a second radiant source characterized by a second average excitation wavelength that is different than the first average excitation wavelength; a sample disposed to receive radiation from the radiant sources, the sample comprising: a first dye; a second dye; and a third dye; a first dye; a second dye; and a third dye; a detector configured to measure emissions from the sample; a first emission spectral element characterized by a first average emission wavelength; a second emission spectral element characterized by a second average emission wavelength that is different than the first average emission wavelength; at least one processor comprising at least one memory including instructions to: illuminate the sample with the first radiant source and, in response, measure emissions from the sample using the detector and the first emission spectral element and measure emissions from the sample using the detector and the second emission spectral element; illuminate the sample with the second radiant source and, in response, measure emissions from the sample using the detector and the second emission spectral element; illuminate the sample with the first radiant source and, in response, measure emissions from the sample using the detector and the first emission spectral element and measure emissions from the sample using the detector and the second emission spectral element; illuminate the sample with the second radiant source and, in response, measure emissions from the sample using the detector and the second emission spectral element; wherein at least one of the dyes is an off-axis dye, an "off-axis dye" being a dye having a first maximum absorption or excitation wavelength that is an absolute maximum over an entire spectrum of the dye and having a second maximum absorption or excitation wavelengths that is a local maximum and is separated from the first maximum absorption or excitation wavelength by at least 60 nanometers; and wherein each radiant source is characterized by electromagnetic radiation within the visible light range, near infrared range, infrared range, or ultraviolet range.