The flag of Israel features a blue star of David that is bordered on top and bottom by a horizontal blue stripe. There is no official blue used in this flag. It is described as "Deep Sky Blue" - which, considering that many flags have specifically designated colors, is a little vague.
Overall, the white of the flag symbolizes light, honesty, innocence and peace. The blue symbolizes many things, including the values of trust, loyalty, confidence, wisdom, confidence, intelligence, faith, truth, and heaven.
The blue stripes are intended to be reminiscent of the Jewish prayer shawl, the Ashkenazi Tallit, which is white with blue stripes. The star of David is a Jewish symbol which was adopted by the First Zionist Congress in 1897.