If you can make a raster PDF proof from your RIP system, try ripping each version with black turned off. Produce a PDF proof from each. If the RIP system doesn't put metadata in the PDF (e.g., the date and time of processing), you should get identical files for each proof if the rasterized results are identical. If each PDF proof is identical, the CMY is identical.
To verify that the PDF proof files are identical, generate a hash from each, such as MD5. If you have a Mac, you can do this with a command in Terminal.app: md5 <filename>. You can drag the file into the terminal window to fill in the file path automatically. There are also online file hashing services, such as
Hash File Online | Hash Value Calculator & File Hash Checker. A hash is a fixed length string that verifies data is identical if the hash is identical (barring malicious interference in the case of compromised algorithms such as MD5). You don't need to carefully verify each character of the hash - a single bit flip anywhere in the data will produce a completely different hash.
If your RIP system doesn't produce consistent raster PDF output, you can export all images with Acrobat, generate hashes for each image and compare the hashes. If you have a Mac the md5 command can also be used to hash the individual hashes and quickly verify an entire folder full of files. Export each version as images to a separate folder. Make sure you use the same base filename when invoking the command to export all images from Acrobat. If one version has filenames like "version1_Page_1_Image_0001.tiff" and another is "version2_Page_1_Image_0001.tiff" you won't get the same hash for the entire folder even if the files are identical. In Terminal.app, cd into the folder for one of the versions and execute this command: md5 * | md5 - that's a pipe character in the middle. This will hash each file, then hash the list of hashes. If you get the same hash in each version's folder, they're all identical.
