Comparing fluorescence intensity of finger print residue after 5 contacts

I have an image as follows that shows the residue of fluorescent powder left on a surface after 5 sequential contacts. Is it possible to quantify the a difference in the amount of residue between contacts?

I have looked at Fiji/ImageJ and selected each finger print at a time to get the mean grey value but I don't see much difference to be honest. Any help or thoughts would be very much appreciated. Happy to think about python or matlab.

In order for the quantification of the intensities to be useful, I would imagine you would need to assume your image was evenly lit and that any fluorescence you see isn't a result of oversaturation. That being said, in principle, you could contour the given fingerprint, duplicate it to a new image, and then measure the stack histogram after adjusting the threshold such that regions darker than your fingerprint powder are set to black. Perhaps the change in distribution will illustrate the change that occurs, if any.

Edit:

First: merge the RGB channels by adding them to one another using the channel calculator function. Your signal is the result of multiple colors, so splitting it does not make sense to me here.

The steps would then be:

1. Duplicate your given print to a new window.
2. Use "Adjust Threshold" to set a threshold of 0-n, where n is the highest intensity that doesn't include your fingerprint.
3. Run the command "Edit/Selection/Create Selection."
4. Run the command "Edit/Clear."
5. Press "ctrl+H" to measure the histogram of the pixels, and then "List" to get the actual values.
6. Repeat for each print and plot on the same chart.

When you are already obtaining the actual histogram values, and not just the range from the particle analyzer, then I'm not sure there's much else that I can personally suggest.