Off-color language can be used as a tool to lash out at others. A person that has mastered the english language can be more effective in presenting their side of an argument without using off-color language. Peer pressure can cause someone to use off-color language, but again, by just saying "NO" to participating, you will earn the respect of others and become a leader. Using this language is being disrespectful of yourself and those that hear you use it.
Your own friends will respect you less if they hear you use off-color language, but they may not say anything to you. They may quietly decide that you are not a friend that they desire to be around because of your actions and will just stop seeing you as often. They may also tell others about your poor conduct and others will respect you less. The following books may be of assistance in learning how to curb your tongue.