selectionColor is part of the parity feature, that needs to be implemented in fabric.
For RN upstream this is an Android prop and hence not part of the baseprops for their respective design.
To implement this in Fabric we need to fork upstream BaseParagraphProps(h/cpp) and include the prop.(As we cant
make this change upstream as RN docs clearly mention it to be Android prop ref: RN Doc )
Note: This used to work for paper because selectionColor prop in JS is delivered to C++ ViewManager code under the same name without transformation. There is no “middle layer”—the string mapping is direct.