The shirt? The tie? The suit / jacket?
These days, I prefer to let the tie (and occasionally, the suit / jacket) do the talking; this means I require shirts in highly neutral tones, of which sky-blue is my go-to. Except for a very pale purple gingham-check twill, all I ever wear these days is blue shirts (plain or consertively patterned).
Don't get me wrong; I'm not advocating loud, satiny ties or overly fussy jackets.
I AM saying that I prefer the tie or the jacket to have more 'visual interest' than the shirt.
An overabundance of visually interesting garments or accessories in any ensemble leaves the eye confused as to where to look, and ruins the entire effect.