You have to hit the "preview" button to see all the fancy formatting buttons like the code # button.
Forget that stupid "Blink" sketch. This is why I hate that they start teaching us newbies to use "delay()". Without using something like interrupts, you can't easily fade an LED during a delay().
Go into the second Examples folder, Digital, and open "Blink Without Delay".
There is a mistake in there.... Change this:
long previousMillis = 0; // will store last time LED was updated
unsigned long previousMillis = 0; // will store last time LED was updated
Now what happens:
millis() is a timer that starts counting milliseconds since the Arduino was last reset. That little fix above makes it so it keeps working even when it rolls over. The variable "interval" sets the length in milliseconds between turning the LED on or off.
You'll want to modify this to your purposes. It appears you want the white LED on for 15 hours, and the blue LED on for 9 hours. Easiest but not the most convenient way to set this for a start time is to have it begin when you reset the Arduino, and just reset it when you want the white LED to start.
I've given you a start. It is late, and I am tired, and I am also a newbie at programming Arduinos.