Blue PMS 282 and Red PMS 193 (US)

An article about the colors at creativepro.com
(one image in the article states that blue is PMS 281)

I guess it depends on who you ask check here and scroll to the bottom.

Pantone Colors for the U.S. Flag

The U.S. Government Printing Office specifies Pantone 186 and 288 for the red and blue colors of the United States flag, but Pantone specifies Pantone 193 and 281. Other sources specify Pantone 282 for blue. This may be because inks look different on different paper stocks.

As for the british flag, one site says PMS 280 for blue and PMS 186 for red.