The top flag may be a blue Peter, but I think the slowing to a stop interpretation makes more sense. I’ll bet you a nickel this strip is printed on newsprint using a limited color process that can’t reproduce blue, so we may never know. (I imagine if they could it would have been used in the water at least a little bit.) That was extremely popular in the '60s and '70s to keep costs down, and there are tons of ads out there from those eras designed around one or two color printing. I also had a pile of children’s books from back when which did the same and forced the authors/artists to make some… strange… color choices and omissions.

The registration is also exceptionally awful here and reveals that they’re apparently only using black, magenta, and yellow. I imagine Jucika’s kayak is actually meant to be red, and it would be except for the registration miss:

That’s also why the polka dots are falling off of the fabric…