Exgratia & All -
I hate to keep doing this, but there's a book on this very topic. It's The Insider's Guide to Getting a Big Firm Job.
PS: As to both pocket squares and pink shirts, no and no. Not even a close call. Do you want to make a fashion statement, or do you want the job? Paradoxically, to get the job, you want the opposite of attention to your appearance. You want the interviewers to not even know why you look so sharp. Just that you do.
PPS: But don't take my word for it. Here's a colleague who, as it happens, wrote the foreword to Insider's Guide: "Personally, I was as clueless as can be during my interviews in law school. Some of my missteps mostly seem cute in retrospect, like wearing a carefully fluffed bright red pocket-square during interviews. I was new to wearing suits, and had no idea about the finer points – I thought I looked quite dapper. Other missteps were more egregious, and almost certainly cost me several call-back opportunities, like taking interviewing tactics from Grisham’s The Firm (the book, not the movie). Lo and behold, reality is different from fiction."