3 Letter Word Riddle

#177

I am a 3 Letter word, 
But uttered by a single letter only.
I am a palindrome,
But, there are only 2 letters in me, 
I am Gray, Blue and Black.
Can you Guess, Who am I ???

  Difficulty Level - 3/5

  For Solution : Click Here     
  For Hint : Click Here      

Who Am I Riddle

#162

In some situations, I oppose the motion 
In other situations I facilitate the motion but, 
I always oppose the relative motion between the two moving surfaces.
Put some lubricant and I become smaller making the moving surfaces rough, 
I make the movement tough I may be static sliding or rolling but whenever two surfaces are in motion I am always there. 
Tell me who I am.. 

  Difficulty Level - 2/5

  For Solution : Click Here     
  For Hint : Click Here