Kleancolor Cobalt is a nice bright blue that's opaque in just one coat. It goes on like a dream but seems to take a bit longer than average to dry. I've found that with all the Kleancolors I've tried though.
It's not quite as vibrant or as opaque as the Kleancolor metallics I have but it's pretty close. Can you believe this is just one coat with not top coat! I always wear a top coat but have plans to layer something else on this so no top coat yet. Such a beautiful blue.