Spectacle Mage’s second ability can’t reduce the colored mana requirements in spells you cast.

Spectacle Mage’s second ability only looks at the mana value of a spell, not the cost you’re paying for it. For example, if you control two Spectacle Mages and cast a sorcery with mana cost {4}{U}, the cost will be reduced to {2}{U}.

If there is an {X} in the spell’s mana cost, use the chosen value for X to determine its mana value. For example, if you cast a sorcery with mana cost {X}{U} and choose 4 for X, its mana value is 5.