Blue
Ravenous Bugblatter Beast of Traal
The rules support this: "At 1st level, you have struck a bargain with an otherworldly being of your choice:" (2014!PHB pg 107)The player chooses their patron, from within a very board range of parameters.
The rules negate this: "Work with your DM to determine how big a part your pact will play in your character's adventuring career." (2014!PHB pg 106)The player decides the nature and terms of the pact.
The player cannot unilaterally decide this according the the PHB. They are one voice in the decision, not the only voice.

