Towards the end of October Hindus celebrate Rams victory over Ravan this is known as Dusshera. Its best that we avoid the term Dushera when referring to Smaghams the same way we avoid using the word Diwali when celebrating Bandhi Chhor.
The Gurbani quote you provided is referring to Holi the Hindu festivel. Guru Sahib says his holi is serving the Gurmukh saints. THe same way his pilgramage to 68 holy places of Hindus is the the giving ( chanting) of naam.
ਅਠਸਠਿ ਤੀਰਥ ਸਗਲ ਪੁੰਨ ਜੀਅ ਦਇਆ ਪਰਵਾਨੁ ॥
This doesnt mean Guru Sahib celebrated holi or went on hindu pilgrimages. Holla Mohalla is distinct from Holi. Holi is a Hindu festivel which Hindus flow colors on each other. Holla Mohalla is a Sikh celebration in which SInghs throw shasters at one another exhibiting their martial ability. Dushera is a Hindu festivel and has no place in the Sikh world. Once again to avoid confusion we should avoid using the name of Hindu Celebrations when celebrating Sikhi. THe panth is already struggling in teaching people the difference between diwaili and bandi chhor. Why throw in another obstacle?