Cannot change color of gridlines with panel.grid

[eliocamp]

The panel.grid argument seems to ignore the color argument (and probably arrow) from element_line()
Minimal example:

library(ggplot2)

g <- ggplot(cars, aes(speed, dist)) +
   geom_point() 

new_line <- element_line(color = "blue", 
                         size = 2,
                         linetype = 2,
                         lineend = "round", 
                         arrow = grid::arrow())

Changes all attributes, but not color.

g + theme(panel.grid = new_line)

Going higher up the inhertance tree doesn't work

g + theme(line = new_line)

But going down does.

g + theme(panel.grid.minor = new_line)