Hmm, think that is Measure 22? Or an early Measure 12?
Whether that's 5-NB or 5-N, then that life ring is lighter than #6 gray; perhaps red? Hard to say.
Notice how light the big paravane is amidships; yet about the same tone as the topsides of the 26' MWB, and both lighter than 5-H topsides. So, that paravane might be white. The after paravanes could be a matt yellow
Taking my magnifying glass to the image, the red stripes are not much help, and the the depth charges are typically flat black. I'll guess that there is a possibility that the lifering is a denim or dark chambray collor similar to the fabric used on kapok life jackets. The blue-grey would contrast against the haze gray some.