Everything fairly close once you WB between the Non filter image to the two ND filter images but again as you can see blue skies get bluer with the stronger ND filters. the only thing that makes sense to me is IR color bleed in the filters gets stronger as well.
Now this test may not be exactly for you and your needs but I like the test for myself of course because now I know what to expect but I think its good overall to understand what ND filters can do. BTW I think the first shot was 1/160 of a second, ND 1.8 was 1/8th of a second and the ND 3.0 was 6 seconds. So if your doing water type things this gives you a good idea of the timing all shot at F8
On to next test and thats shifting