In my experience over the past 27 years, nearly all male clients ask for red lettering.
They always feel that it is the most eye-catching color.
So give him the red he wants, as a background color.
Then add white lettering.
Like a stop sign, it's going to stand out and be legible at a distance.
Also, in my experience, caps and lower case are easier to see than all caps, which can look like just a block of text at a glance.
Which one reads better from the thumbnails, yours or mine?
Not saying that mine is a masterpiece, just a quick example.
Here's a suggestion, using clip art, because I am too lazy to dig up a caduceus.