> Dark brown is not the ugliest color, the ugliest color is magenta.
That's just, like, your opinion. Beauty is subjective and the only way to declare something the ugliest, in some general sense, would be to get the subjective opinions of many people. This is presumably what was done in the market research for Pantone 448 C.
Also, magenta stands out. That is a likely reason why it was chosen as a transparency placeholder, rather than just being "ugly."
Try offering a reasonable (big enough for people to consider and not big enough for then to agree to everything) reward for people to set #FF00FF for their computers and phones (and keep it for e.g. a month) background colors and see how many are going to agree. I can bet much more people will agree for Pantone 448 C.
That's just, like, your opinion. Beauty is subjective and the only way to declare something the ugliest, in some general sense, would be to get the subjective opinions of many people. This is presumably what was done in the market research for Pantone 448 C.
Also, magenta stands out. That is a likely reason why it was chosen as a transparency placeholder, rather than just being "ugly."