The short answer is that I don't know. The pattern is vaguely similar in shape to one of the standard designs in CB.3098 from May 1943, but not a match. Furthermore, the relative tones do not match particularly well with that design either which has larger gaps with the darkest colour being G10.
A friend in the USA is building a 1/350 model and asked the same question 2 or 3 weeks ago. I did this at that point to *suggest* colours which might fit well with the observed tones. I used a well known photograph, plus the free online colour summarizer tool "mkweb" to analyse a segment of the bow, then calculated Light Reflectance Values (the Y part in Yxy colour space) for each of the 3 tones on the hull. They are 15% apart and the absolute values corroborate reasonably well with B15, B30 and G45.
Attachment:
Saumarez2.jpg
No promises though...