I use a 4-digid display with a single colon in the center. The colon is not displayed when I have the leading zeros parameter set to false, and the value is zero.

red.showNumberDecEx(hour(), 0b11111111*(second()%2), false, 2, 0);
red.showNumberDec(minute(), true, 2, 2);

It works correctly for any other value than zero, but if hour() in the above example is 0, the colon does not show. This seems to me like a small bug.