stick with black, navy blue or gray suits, they are the only ones of accepted color, if you wear a navy suit then black shoes of very conservative 2 or 2 1/2 inch heels are acceptable. I recommend that the scarf be smart and silk from a respectable store like brooks brothers and if you can't afford their pricing then look on ebay.. if you can afford better then go for an hermes scarf because they specialize in making them for decades. Try to take an appointment and have a fashion expert in a particular store get back to you with good matching pieces. Tell them exactly what you want. Whenever I shop for a suit I have a talk with someone about the occasion and what I am looking for, that way if they don't have an item in the store they'll call and get it for you. (it is a free service) for wide leg pant suits I'd look into anntaylor.com or jcrew.com
I'd pair any of the above colored suits with either a crisp white blouse/shirt or a light pink (goes really well with gray) navy blue can also be coupled with a lighter blue shirt..
All the best for your interview insha'Allah