Light from Within

• WWizards of the Coast2008-08-01
  Official Ruling
  Chroma abilities check only mana costs, which are found in a card’s upper right corner. They don’t count mana symbols that appear in a card’s text box.
• WWizards of the Coast2008-08-01
  Official Ruling
  Light from Within affects each creature individually. For example, if you control a creature with mana cost and a creature with mana cost , the first creature gets +2/+2 and the second creature gets +5/+5.
• WWizards of the Coast2008-08-01
  Official Ruling
  Chroma abilities count hybrid mana symbols of the appropriate color. For example, a card with mana cost has two red mana symbols in its mana cost.

Rulings via Scryfall