All people prefer colors that they can distinguish easily to colors that they have difficulty distinguishing.
Statements
All people prefer easily distinguished colors to tough to distinguish colors.
Infants can easily distinguish bright colors, but find it tough to distinguish subtle shades.
Adults do not find it tough to distinguish subtle shades.
Brightly colored toys for infants sell better than the same toy in subtle shades.
Evaluate
The overlapping ingredient being discussed in the first two sentences is "easy vs. difficult to distinguish a color", so we should pause to synthesize what's going on there.
Since we all prefer easier to distinguish colors, and infants think bright are easier to distinguish, then infants prefer bright colors.
We don't know what adults prefer, because we only know that they might prefer subtle shades (since they don't find them tough to distinguish).
The last sentence sounds like a manifestation of our Inference. We had inferred that "infants prefer bright colors", so it makes sense that a bright colored version of Toy X sells better than the subtle colored one.
Does this mean that the infant got to pick out his/her own toy?
Not necessarily.
Goal
Let's find the most provable option, probably something that reinforces the idea that "infants prefer bright colors".