Dialogue
From Mass Effect Wiki
Dialogue in Mass Effect is being touted as "the real star of the show." [1] Instead of the traditional dialogue choices, which show you every word of your response verbatim, you are presented with choices that can be described as gut feelings. For example, one of your choices may be "Don't try to study me," but what your character actually says is "I'm not some artifact you can take back to your lab, doctor."
NPCs can be influenced by the use of Charm or Intimidate. In the dialogue tree, charm responses are colored blue and intimidate responses are red. Use of those skills is affected by the character's morality. However the richer the colour the more likely charm or intimidate will work; conversely, the lighter the colour the less likely it is to work.
The conversation wheel was designed so that dialogue options that progress the conversation forward are located on the right side of the wheel and options such as "Investigate" where relevant questions can be asked about the current situation reside on the left side. The choices for the right side of the wheel are ordered in severity from lightest (Paragon morality) at the top to strongest (Renegade morality) at the bottom. In addition, some dialogue choices affect events that occur during and even after the dialogue; for example, if you run into a hostage situation, using the Charm choices may avert the situation without any bloodshed at all, while the Intimidate (or even the standard) choice may lead to violence on both Shepard and the criminal's part.
