Why is Saturday Blue and Sunday Red for Seiko?

Good point! never wondered why but I would like to know myself…maybe blue for the end of the week and red for beginning of the week? 
 

did some research here’s what I found…

I don’t care if Monday is blue, Tuesday is gray and Wednesday too…

damn you Reddit!!!!

I'm pretty certain the red is a day of rest/holy day thing. On the English wheel, Sunday is red, on the Arabic wheel it's Friday.

I don't think the blue Saturday is universal but I'm not super well versed in random Seiko lore.

The red Sunday is not only Seiko, but I have never seen the blue Saturday on another brand. Pretty sure the red Sunday is for Christianity, especially considering that Friday is the day that is red on the Arabic dial, and that would correlate with the day of worship for Islam. One supposition I did see on a reddit thread for the blue Saturday was the idea that it is for the Jewish Sabbat, as the shade of blue is associated with the state and flag of Israel. I am not sure if that is true, but it is a hypothesized reason.

Obviously, red is to warn you of the impending Monday. Sunday Scaries, ahhhhhh! 😉

During mid 60s there were school and work on Saturday until lunch in my country. No ”red day” then.

https://www.543life.com/campus115.html

Origin of Sunday and Monday Beginning

The fact that Saturdays are now blue is related to the so-called two-day week. Triggered by the first oil crisis in 1973, more and more companies closed on Saturdays amid a growing mood to save electricity. In response, many calendars began to display Saturdays in blue from the 1974 edition. In general companies, the two-day work week system gradually took root after that, but it was not until 1992 that national public servants became two days off per week. Public schools are 10 years behind in 2002. In this way, the two-day work week system gradually became widespread, so it is presumed that the calendar kept pace with it.

Next, we must answer the question of why it is blue. It seems to have something to do with printing technology. This is because the four primary colors of printing are yellow, red, blue, and black, red is used on holidays, black is used on weekdays, and the rest are yellow and blue. Yellow is less noticeable when contrasted with the color of the ground. Blue, on the other hand, is clearer, if not as much as red or black. Of course, there is an option of composite color, but there is a disadvantage that it tends to cause color shift. For these reasons, blue was chosen as the third color, probably due to the course of nature.

In the United States and Brazil, Sundays and holidays were red, but Saturdays were the same as weekdays. In other words, it doesn't give much meaning to Saturday. In China, Saturdays and Sundays were red or pink, Saturdays were green, and Sundays were red. What was surprising was that in the Chinese Buddhist and Taoist calendars, only holidays were colored, and the rest were black regardless of weekdays or weekends. In the Korean Buddhist calendar, weekdays and Saturdays were black and Sundays were red, but blue was used for lunar calendar dates.

There were examples in the Jewish calendar where weekdays and Sundays were black, and Sabbath Saturday was blue. In the Islamic calendar, there were those that made Friday of mass worship days red, and university calendars that made Thursdays and Fridays without classes red.

Turning to Southeast Asia, there are calendars in Vietnam and the Philippines with Saturdays in blue and Sundays in red, as in Japan, while there were also two-color prints for Chinese-Indonesians in Myanmar, with blue weekdays and red on Saturdays and Sundays.

It's just a lot of things.