Hanuma had returned from Lanka after seeing the distraught Sita Devi and informed the same to Lord Rama. With no further delay, the Lord began his journey to Lanka from
Rameswaram. en route, He encountered the great ocean between mainland India and Lanka.
He prayed the Samudra Raja (King of the ocean) to let Him and His vanara (monkey) army
pass through it. He waited for three days and nights. Finally, seeing His army getting
depressed Lord Rama shot a number of arrows at the ocean, which startled and woke up the King of the ocean. He saluted the Lord and said that a bridge(setu) could be built over it by Nala and Neela, the architects in the army of Lord Rama. This is how the Lord got the name 'Seturama'.
All the chieftains of Lord Rama's army including Hanuma, Jambavan, Nala, Neela, Angada, and Sugreeva began building the bridge post-haste. They smashed huge mountains which
were nearby and took the huge rocks and hurled them into the sea.
The ocean bank was abuzz with activity of the monkey army, who were busy filling the sea with huge stones. They were piling rocks in order to create the bridge to Lanka.
At this time a squirrel was watching all the activity. It saw Lord Rama, and like all us
who have a glimpse at Him, was highly inspired to support His activities. So it piled little
loads of sand, mud, and pebbles on its tiny back and began filling the gaps between the huge boulders so that the feet of Lord Rama would not be hurt while walking on the bridge.
Lord Rama saw the sincere efforts of the squirrel and picked it up in his hand and
caressed it with his fingers. The squirrel, which was fully grey in color till then, got four
white stripes on its back because it had been touched by the divine fingers of the Lord.
This is how we believe the squirrels we see today have both white and gray stripes on their backs.
Moral: we may be very small people in this world, but in our own little way, having good intentions at all times, we must always support the mission of the Lord, without thinking of the eventual result or outcome, and thereby receive his divine blessings.