Star Testing:Green vs. Yellow filter

I have an older FPL53 Triplet that when star testing shows almost two different test depending on which filter I use. With the yellow filter the star test is funtionally perfect. Nice symetry, equal intensity of rings on both sides of focus. With the green filter the rings are asymetrical and don't look good at all. I heard that achros shoud be tested with green filters and FPL53 should be tested with yellow filters. Is this accurate or is my lens flawed?? Thanks