I suppose that if you want a road to be durable and long lasting in a recursive land you make it out of something Yellow so that it changes the least and is as stable as possible. But even a Yellow Brick Road that laughs at limits and boundaries won't take you over a river unless you have a Yellow Brick Bridge.

They do get across, even though the Scarecrow was afraid he had returned to where he started, stuck on a pole again and even more useless than before. Saved by a Stork. Like a rebirth?

On the other side they run into the Red poppies of Death. Poppies imply opium and thus recursively never-ending sleep. Perhaps the poppies don't affect the mice because the mice are beneath the flowers. Lowly mice, yielding mice, bringing the scent within themselves back on the scent within themselves. Perhaps.

Hereabouts wearing green spectacles won't make everything green except for a little while. Then our eyes adjust and we see other colors quite clearly though they would have a faint green tinge. In Oz potentials are actuals so it might be that a lot of what was originally some other color became green just 'cause it looked green. At any rate the Guardian of the Gate had green skin even before they put the spectacles on.

Dorothy saw a Head, the Scarecrow a Lady, Nick a Beast and the Lion a Fire. Each was hope to the one that followed. The brainful Head was hope to the Scarecrow, the heartful Lady was hope to Nick, the terrible Beast was hope to the Lion. And then, that which all animals fear, Fire was fear to the Lion so he got a double dose of hope and fear. How very recursive for a humbug Wizard.