Regarding the statement below how accurate is it on describing why dyes such as Pinacyanol chloride and Pseudocyanine iodide look a certain color:

"A dye is something that is used to change the color of something, and this is done because the PI bonds in the carbon chain and the nitrogens are overlapping are hit with a specific wavelength and absorb it. Then some time after, the electrons fall from the LUMO back to their original HOMO emitting a photon that happens to be in the visible spectra due to coupling and resonance making the HOMO and LUMO fall in that range. The specific wavelength of photon emitted is then seen as visible light that the spectrophotometer picks up as a wavelength with high absorbance."

I hear that some substances look a certain color because they reflect certain wavelengths BUT in chemistry I hear that electrons in molecules get excited to the LUMO and emit light once going back to their normal state, so which is correct? which is correct for the explaination of Pinacyanol chloride and Pseudocyanine iodide?

Also, why would measured and calculated values in wavelength and absorbance differ? just some bulletpoints will work for this one