"sky had fanned into a thousand shades of yellow and orange"
The sky was lit in colours from the sunset.
The colours appeared to radiate from a point, probably where the sun was, or had been, in the way a fan, as in asian hand fan, radiates outward from the handle.
"A latched gate gave way to steps that descended to a planked walkway over the grass.
There was a gate.
it was latched, had a latch mechanism to keep it closed, until opened.
Beyond the gate were steps down to an area of walkway made of wooden planks, boards, which was above grass. the walkway was above grass, had grass underneath, or possibly lower than the walkway.
Hope this helps.