For an occasional suit that you want to rely on for more formal occasions such as a job interview, go with the charcoal or dark gray. If you wear it infrequently, you will look sharp and draw approving looks. I mean that people will notice you, especially around the office.
You can supplement the suit with a smart sport coat in navy or light to medium gray. You should think about a sport coat with some texture, a small check pattern or glen plaid. You can match the sport coat with chinos, dark jeans, or odd trousers (gray flannel etc.). It's great for a night out when you want to dress up or for the business casual office. A well tailored jacket will always improve your appearance.
If you want some flare, you can also pick up a vest (waist coat). Again, it goes well with chinos or odd trousers and a button down oxford with or without a tie. You'll make an impression and stand out from the crowd (if that is what you want).