R – Emulate ggplot2 default color palette

Change the last line to

q + theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust=1))

By default, the axes are aligned at the center of the text, even when rotated. When you rotate +/- 90 degrees, you usually want it to be aligned at the edge instead:

The image above is from this blog post.

You must put colour = rhg_cols inside aes(). As far as I can tell, you want to apply gradient to bars (in barplot) with factor variable on the abscissa? Then use fill - try this instead:

ggplot(mydata, aes(factor(phone_partner_products), fill = factor(phone_partner_products))) +
  geom_bar() + 
  scale_fill_manual(values = rhg_cols)

or try to achieve approximate replica with:

ggplot(mydata, aes(factor(phone_partner_products), fill = phone_partner_products))) +
  geom_bar() + 
  scale_fill_gradient(low = "#771C19", high = "#000000")

Notice that in second case a continuous variable is passed to fill aesthetics, therefore scale_fill_gradient is passed afterwards. If you pass a factor to the fill aes, you must stick with scale_fill_manual(values = rhg_cols).