Can aluminium form blue-colored solution in liquid ammonia? I am a high school student and in one class, my inorganic chemistry teacher told group 1 elements with the exception of lithium and group 2 elements with  exception of Be form blue-colored solutions in liquid ammonia (Mg requires an electrolytic process). What are the conditions for a metal to form a solution in liquid ammonia, and which metals (other than what I have mentioned) form blue-colored solution in liquid ammonia? Can aluminium also form such solution?
The SE answers quoted in the comments provide a good broad answer but with respect to the question of aluminium – aluminium will form a blue solution in liquid ammonia following electrolytic reduction of $\ce{AlI3}$ in liquid ammonia according to J. Am. Chem. Soc. 1950, 72 (11), 5178–5180.
Europium and ytterbium have also been reported to dissolve in liquid ammonia in J. Phys. Chem. 1956, 60 (11), 1590–1591.