Khanda on Sikh flag and Kesari color.

[New Sikh Ekab Singh]

As per my understanding

...Khanda on Sikh flags is a recent addition and is not a symbol given by Guru ji. please  see post by by Serjinder Singh  https://www.sikhnet.com/discussion/viewtopic.php?p=12326.    The current Khanda began to evolve after the British occupied Panjab. A new battalion known as Rattray's Sikhs which became 45 Sikhs of the British Indian Army was set up soon after 1849. The soldiers of this battalion used to have an insignia pinned on the front of their turbans that was just a circle or a chakar on the top of which there used to be a khanda standing upright with the handle of the khanda touching the upper edge of the Chakkar.

 

... Kesari color was given by mahants to assimilate Sikhs as Hindus to bhagwa color of Hindus.... As far as I know  first 5 Guru ji had a white flag ...6th Guru gave us yellow color and he called the flag Basanti ...10th master gave us blue.... Why do we have rituals for them I dont know... we are suppossed to be out of rituals....

[EKawaaz]

During the times of Guru Amar Das the Nishan Sahib was white, to represent peace and simplicity. During the time of Guru Hargobind, however the Nishan Sahib mas made into a shade of yellow, known as Basanti, to show the spirituality of the Sikhs and their warrior spirit. After the creation of Khalsa, Guru Gobind Singh introduced Navy Blue (called Surmayee) flag, which is still the colour of the Nihang flags. The first Sikh flags were plain, but emblems were introduced by Guru Gobind Singh. The first Sikh emblem, was not the Khanda, but the three weapons, the Kattar (dagger), Dhal (shield) and Kirpan (sabre). Later these emblems were also used by the Sikh misls and the Empire.

When Gulab Singh asked Maharaja Ranjit Singh to change the Nishan Sahib to saffron or deep orange Maharaja Ranjit Singh declined but later when he changed the army from traditional Akalis to French-style soldiers he made separate flags to respect Hindu and Muslim^[1] ideologies. Later the Battle standards for Muslim regiments was the Lion and the Sun and the Hindu Regiments were various gods and goddesses.https://en.wikipedia.org/wiki/Nishan_Sahib

Later during the British Rule it became from Basanti and Surmayee to Kesari and Surmayee due to the Hindu Mahants, Nirmalas and lack of historians. This influenced Sikhism a lot and it became the Kesri Nishan Sahib with a peacock feather on top.

During the Singh Sabha Movement the Sikhs tried to restore Sikhism to its pristine glory so in the start it became the Flag of the Dal Khalsa but slowly it changed to the today's Nishan Sahib with the Khanda Emblem.

[Soulfinder]