Maybe it was the Summer of Love? Things of Science started to get more colorful in 1969 — swapping out the usual yellow-gold paper for other colors (although admittedly, a less-than-inspired gray here) .
Additionally the “logo” for Things of Science changed as well. See for yourself on page 1 of the booklet linked below.
This unit takes on geometry but explains some familiar concepts in a hands-on way. Very cool.
Here is the booklet:
The last few pages of the booklet contain scans of the cards that came with this unit. Additionally there was string, a push-pin, etc. Contents here:
More Things of Science scanned here.