Choosing same color after Wild (+4)
These rules appear to be from 2001, and these rules appear to be from 2003. Both sets of rules do not indicate any restrictions on the choice of colour after either wild.

The points from both rules about Wild Draw 4 are:


  
  You play it and choose the colour to continue.
  The next player draws 4 and misses their turn.
  You can only play this if you don't have a card of the matching colour.
  You can break the above rule.
  The person drawing 4 may challenge you. If they win, the you draw 4 instead. If they lose, they draw an additional 2. (Note that they still miss their next turn)
  


Neither set of rules have any limitation on the colour choice.

For further reference, there's this question regarding the history of UNO rules. The 1983 rules found there follow the same draw 4 rules as the more recent rules printings.