A pair of young ladies - twins, actually - suggested that Bob use this mix of pastels while they were watching the glassblowing one day. The Morgan-Taylor mix has been a staple ever since, just popular enough that we keep thinking we should have more pastel mixes.
Since each Float is absolutely unique, there will be some variation in appearance. Below are some photos of Floats of various styles over time with these colors, to illustrate what kind of range there might be: