In a bowl of a stand mixer fitted with the paddle attachment, whip up the butter until it's light and fluffy.
Add in the salt, vanilla, pumpkin spice, and heavy cream and whip up again until combined.
Slowly add in the powdered sugar with the mixer on low speed and about 1/2 cup at a time. Add in more heavy cream if needed (about a Tablespoon at a time).
Reserve 2 cups of the pumpkin spice buttercream in a separate bowl and add in the orange gel coloring to tint the buttercream a soft orange. Add the buttercream to a piping bag with the end snipped off.
With the rest of the buttercream add in the cocoa and mix until it's fully incorporated.
Stack and crumb coat the cake using the cocoa buttercream (making sure you have enough left for the final stripe layers. Chill to set.
Add on the rest of the cocoa buttercream to the outside of the cake, then use a stripe cake scraper to make clean indents in the sides of the cake. The cleaner the stripe, the neater the stripes will be. Chill (freeze) about 10 minutes to make sure the buttercream is firm, then pipe in the orange pumpkin spice buttercream stripes. Using a flat cake scraper scrape pressing firmly) the stripes until the clean stripes start to show through from underneath. Add more buttercream where it's needed, and scrape again until the stripes are clean. Enjoy!