I have 2 iMacs, each running Motion v5.3.2 and FCPX 10.3.4. On the older iMac, in FCPX I found that the built-in FCPX Generator named "Custom" in the Solids generator group no longer has the color picker on its Published Parameters tab in the Inspector.
In Motion 5 on that iMac, I selected Add Object > Generators > Image Generators, and found that its list of image generators contained only two entries: "Cellular" and "Noise". On my newer iMac, running the same version of Motion, the list of Motion's built-in Image Generators contains 28 entries, from "Caustics" to "Two Color Ray".
On the older iMac, how could Motion's missing 26 built-in generators disappear? Can I copy the missing ones from the newer iMac to the older one? If so, where can I find Motion's built-in generators? (On the older iMac I cannot upgrade Motion to the new version 5.4 because that iMac is still running OS X 10.11.6, El Capitan, and Motion 5.4 requires at least macOS 10.12.4.)