'Fear' was introduced with the beginning of the game and it has recently been replaced by Intimidate which is not color specific keyword ability.

702.33. Fear

• 702.33a. Fear is an evasion ability.
• 702.33b. A creature with fear can't be blocked except by artifact creatures and/or black creatures. (See rule 509, "Declare Blockers Step.")
• 702.33c. Multiple instances of fear on the same creature are redundant.

Translation:

• 702.33a - Fear applies to combat in defining who can and can't block the creature.
• 702.33b - Your opponent can only block this creature by using an artifact creature or a creature that shares this creature's color.
• 702.33c - The game doesn't care how many instances of Fear a creature has, 1 is the same as 100.