Performing a side-by-side test method validation will give you the answers you are looking for.  Use a predetermined sample population, having both positive and negative controls within it (0.002 in per the standard for the positive controls), and testing all of the samples using both solutions per the standard.  If the results are the same, then you can use the food coloring solution.

The most frequent thing we encounter during the performance of our tests that cause sterility breaches or failures is when the primary package is folded and placed into another secondary or tertiary package. This can cause undo stress at the points the package is folded over making it more susceptible to failures. The other cause results in not taking into account any obtrusive or sharp edges or points on the product itself and than not properly placing or packing it inside of the primary package.