In “Dead Man’s Path” how do the older and younger generations view life? What accounts for their differing views? Which group or person is right? Regarding symbolism and representation, who represents modernity? traditional beliefs and values? colonialism?

I will focus my answer on the first half of your question on “Dead Men’s Path.” It’s clear to see Achebe sets up two different perspectives on life through two principal characters.
In Achebe’s “Dead Men’s Path,” there’s a stark contrast between the beliefs of the younger, progressive, colonial attitude of the new generation, represented by Michael Obi, and the traditional, African views of the older generation, represented by the nameless village priest. Obi wants to bring the school he’s taking over into the modern era by adopting British reason and leaving old African religion behind. Their two different views are manifested around what to do about the ancient foot-path. You can see their conversation on the last page of the text.

“Look here, my son,” said the priest bringing down his walking-stick, “this path was here before you were born and before your father was born. The whole life of this village depends on it. Our dead relatives depart by it and our ancestors visit us by it. But most important, it is the path of children coming in to be born.”
Mr. Obi listened with a satisfied smile on his face.
“The whole purpose of our school,” he said finally, “is to eradicate just such beliefs as that. Dead men do not require footpaths. The whole idea is just fantastic. Our duty is to teach your children to laugh at such ideas.”

It’s clear in the rest of their conversation that tradition is important to the older generation, and progress is important to the younger generation, until Obi sees what happens when one disregards tradition completely.
https://www.sabanciuniv.edu/HaberlerDuyurular/Documents/F_Courses_/2012/Dead_Mens_Path.pdf