Gadfly, new Color/Layer

Question

When I push new layer to an existing plot, it keeps the same color. Is there a way to change the color automatically when a new layer is pushed to a plot, or at least a way to set the color using a random number (I don't know in advance how many layers I will have) ?

y=[3, 7, 5, 1]
x=[1, 2, 3, 4]
xmin1 = x .- 0.1
xmax1 = x .+ 0.1

xmin2 = x .- 0.5
xmax2 = x .- 0.3

y=[3, 7, 5, 1]
x=[1, 2, 3, 4]
xmin1 = x .- 0.1
xmax1 = x .+ 0.1

xmin2 = x .- 0.5
xmax2 = x .- 0.3

p = plot(xmin=xmin1, xmax=xmax1, y=[3, 7, 5, 1], Geom.bar)

# The following creates a new layer that keeps the same color
push!(p, layer(xmin=xmin2, xmax=xmax2, y=[3, 7, 5, 1], Geom.bar )) 

# I do not want to use this because I don't know how many layers I will have
# push!(p, layer(xmin=xmin2, xmax=xmax2, y=[3, 7, 5, 1], Geom.bar, 
#    Theme(default_color=colorant"green") ))

Answer 1

One possible solution:

Using Colors
function gen_colors(n)
  cs = distinguishable_colors(n,
      [colorant"#FE4365", colorant"#eca25c"], # seed colors
      lchoices=Float64[58, 45, 72.5, 90],     # lightness choices
      transform=c -> deuteranopic(c, 0.1),    # color transform
      cchoices=Float64[20,40],                # chroma choices
      hchoices=[75,51,35,120,180,210,270,310] # hue choices
  )
end

mycolors = gen_colors(n)

at run time you call this function with the number of layers to add in the plot then use elements of the returned array as arguments to default_color. Namely, for the i-th layer use

Theme(default_color=mycolors[i])