Hi @mpenson -
Welcome to the Forum!
I will start by saying... it's best to really determine an analysis protocol on higher resolution images from the start. So if you can acquire those - I would recommend doing so asap. You will need them for any sort of robust analysis - including initial set-up. Saying that...
Can you clarify a bit exactly what you wish to measure in this image? When you say 'intensity of blue' - what exactly do you mean? You can look into the Color Threshold tool in ImageJ. Just know that the same analysis settings need to be applied to all the images you are measuring.
Hope this helps at least get you started.