After updating xts package in R, I encountered the following problem:

Code:

> plot(equity, col = "blue")
Error in axis(1, at = xycoords$x, labels = FALSE, col = "#BBBBBB", ...) :
  formal argument "col" matched by multiple actual arguments
 

Here is a workaround:

Code:

> plot(equity)
> lines(equity, col = "blue")