I guess, your confusion comes from the presence of GLOB slot in the symbol table entry described in the book. In reality, the syntax *{"color"} references the symbol table entry as a whole, not the GLOB slot of it. When you assign some reference to this entry, then perl copies the reference into appropriate slot of the symbol table (type of reference defines which slot is taken).

The GLOB slot of symbol table entry mentioned in the perlref is something obscure. It is not reported by the Devel::Peek module. I guess, that this is just a syntax sugar. One can do either $a = \*other; or $a = *other{GLOB}; and both shall return the reference to the symbol entry as a whole. This reference can be used for reading files and doing something like *{$$a} = \$b; to alias $other with $b.

Reference to the symbol entry is not the same as an "alias" for the symbol entry. You can do $a = *other; here $a shall become alias of the symbol entry and you can say ${$a}[0] = 2; or ${$a}{key} = 3; or <$a> to read the file. All of this will actually use @other or %other etc. Effectively, it is an alternative to using references.