I have a condition on my view that specifies that the date is less than TODAY and I don't specify any color i.e. leave it at FFFFFF. Upon saving, this clears the filter I just applied. This bug wasn't there prior to 4.2 and looks like it has been introduced since then. Could this be pushed to the 4.3.1 release?
I am able to reproduce what you have mentioned with a 4.1.x build too. I have logged a bug for the same, and shall keep you posted when the fix is available.
As a workaround, please set value to FFFFFE for your condition.