I guess you have already found your solution by now.
It is okay to find colourless areas in between the blue plaques, it means the cells there have died in this region.This may happen if you are using an E.Coli culture which old or was above O.D 0.5. You can consider the titration as "passed " and can continue counting the colonies. But if you want to extract the DNA from these colonies then I would advice you to freshly amplify them before beginning the extraction. Hope this helps.