Green and the Mushroom Planet

In Green, leprechauns kidnap Lily Green and put her in a fake rocket ship before taking her to the leprechaun realm. Once there, she finds a letter left for her by her late grandmother, written in green ink. In The Wonderful Flight to the Mushroom Planet, Tyco Bass runs an ad in the newspaper to recruit a boy to build a spaceship to go to Basidium. Although the rest of the newspaper is black-and-white, his ad is printed in green. In Green, the green ink is understandable (they're leprechauns; all their things are green), but the Mushroom People have no special affinity for that color, and it is never explained why the ad was green.

The leprechauns in Green have hair "with the merest hint of green." Likewise, the Mycetians (Earth-based Mushroom People) have just a hint of green in their skin color -- subtle enough for them to pass as human without attracting undue attention.

Both the leprechauns and the Mushroom People deal with security breaches by administering a drink that causes forgetfulness.

The Mushroom People, both on Basidium and on Earth, use Mushroom Stones as symbolic decorations, and there is a hint that they may have used them as money in the past. These are round, flat on one side and convex on the other (like a mushroom cap), and have symbols engraved on the convex side, one of which is always a mushroom. In Green, one of the leprechauns gives Lily the gift of "a domed gold button, a four-leaf clover embossed on its shiny surface." A domed button would have the same shape as a Mushroom Stone; in fact, when I search for domed button, the very first hit is offering "Bronze Mushroom Domed Buttons" for sale. One gets the impression that Eleanor Cameron and Laura Peyton Roberts somehow received essentially the same mental image and interpreted it in the context of their respective fictional worlds.

Here's a description of a Mushroom Stone, from A Mystery for Mr. Bass:

Each amulet was exactly the same size, about an inch and a half across, and all were in the shape of mushroom heads or half-balls. Each had deep lines cut into it on the domed top which crossed at the center so that the dome was divided into pie-shaped wedges, and in each one of these wedges was a different, curious carved design or picture. On every amulet one of these pictures was always a mushroom.

It is not specified how many wedges each Mushroom Stone is divided into, but it must be an even number (since the lines cross at the center), and four to eight seems likeliest -- much more than that, and the wedges would be too narrow to contain pictures. Couldn't such a design easily be misinterpreted as a four-leaf clover, or vice versa?