[Edit:] Dang, I thought I read the thread, but I didn't notice there was similar proposals all ready! [Edit2:] No, on second glance, the similar ideas appeared while I was slowly typing my first idea[/Edit2][/Edit]

Using 4 coulours and three blinks to convey the time at an accuracy of 15 minutes just popped into my head:

The first blink of one of four colours could represent a quadrant of the clock, a second blink of one of three the hour in that quadrant and a third blink could represent 0,15,30 or 45 minutes...

(First I had an other idea, that is not as straightforward, but I'll paste it below, just because I had all ready typed it: If this app will evolve to have loads of different options, one novel idea could be the "Colorful compass clock concept":

With 4 distinct colours, representing North, East, South and West, one could have the blinks indicating what time it is.

One "North" blink would be around 12 o'clock. Two blinks, for example North-East would be about 1:30. East-North-East would be ... around 2:15 (?). With four blinks, one would get an accuracy of 22.5 minutes, with 5 blinks, half that...

This would of course only ever require 2 colours at a time... )