Problem in saving plot when giving color parameter

New to Julia
1

Hello,
I could save a plot using PyPlot, but when I added the custom colour parameter, I could not save the figure anymore:

clf()
myPlot = plot(soln.t, getindex.(soln.u, 1),
              soln.t, getindex.(soln.u, 2),
              soln.t, getindex.(soln.u, 3),
              soln.t, getindex.(soln.u, 4),
              color = ["blue", "orange", "red", "green"])
...
savefig("plot.png", dpi = 300, format = "png", transparent = false)

what could be the problem?