To cut to the chase...
I look at Twitter's usage policy and see limitations on what can and can't be done with their logo.
I also see examples of websites that use icons that have been integrated with the look and feel of their own site. Given Twitter's policy, for example, it would appear that legal conversations/agreements would need to take place to do this, especially on a commercial site.
I believe it is perfectly acceptable to have a plain text button that simply has the word "Tweet" on it, that has the same functionality.
My question is if anyone can provide online (or other) references that attempt to summarize what can and can't be done when integrating various social networks into your own work?
The answer I will mark as the correct one will be the one which provides the best resource(s) giving the best summaries of what can and can't be done with specific logos/icons, with a secondary factor being that a variety of social networking sites are addressed in your answer. Before people point to specific questions, I am looking for a well-rounded approach that considers a breadth of networks and considerations.
Background: I would like to incorporate social media icons and functionality, but would like to consider what type of modifications can be done without needing to involve lawyers. For example, can I bring in a standard Facebook logo, but incorporate my site color into the logo? Would the answer differ if I maintained their color, but add in a few pixels of another color to transition? I am not saying I want to do this, but rather using it as an example.