I have a yellow assessor and two citron clown gobies in my 65g. Both add a nice pop of yellow but ... despite perching 90% of the time ... the clown gobies are actually more visible, more often.
While my assessor isn't shy, it not too comfortable with the constant motion of my wrasses and anthias ... so it prefers to spend the day in its cave and comes out in the evening and at night to swim.
Not saying all assessors will be a slight bit reclusive. But, being that they're found beneath overhangs and in caves, it is in their general nature.