About 23 years ago, I deployed a character based pawnshop management application for MS-DOS 6.22 and Altos Xenix-V platforms.
All my forms use high contrast with a black background. In the pawn transactions form, I display the number of days that have elapsed since the customer pawned their items, or made their last interest payment.
If the number of elapsed days is less than or equal to 80, I display the number in green color. 81 to 89 days in orange, and 90 or more days in red with fast blinking animation.
The conditional blinking attribute in the legacy application is easily programmed with only one line of 4GL code:
COLOR = red blink WHERE CalcExpDays >= 90
MS-DOS and Xenix video drivers support blinking, underline, reverse and invisible video attributes via a system call, but blinking is difficult to implement in Windows and Linux GUI forms, requiring the use of a timer to generate a blinking animation.
