[lagt_t]

You can print concert tickets and photocopy ids in black and white, I don't understand your point. Noone requires color for those use cases.

[lmm]

I've had cases where colour was required e.g. one of my ID stamps was unreadable in black-and-white, my tax return form has colour sections (might have been accepted in black-and-white but was certainly clearer in colour)...

[kstrauser]

I absolutely 100% guarantee that you can submit tax forms printed in black and white. I suspect the IRS is more surprised when they see printed forms that are anything but.