How to manually set the color scale in contour plots R-Plotly?

Question

I'm trying to set a Rainbow color scale in my contour plot, but don't know how to do it. I started my code like this:

p = plot_ly(type = 'contour', z = matrix, 
    x = fracao, y = -prof, colorscale = 'Rainbow', 
    autocontour = F, contours = list(start = 0, end = 12, size = 3, showlabels = T))
    %>% colorbar(title = "Wt. %"))

But after reading this topic... Colorscale = 'Rainbow' in plot_ly doesn't work

I changed my code for:

    p = plot_ly(type = 'contour', z = matrix, 
    x = fracao, y = -prof, colorscale = cbind(seq(0, 1, by=1/(length(z) -1)), rainbow(length(z))), 
    autocontour = F, contours = list(start = 0, end = 12, size = 3, showlabels = T))
    %>% colorbar(title = "Wt. %"))

The problem is that although I got a "rainbow" palette for my plot, it doesn't look good, as you can see below:

How can I set the colorscale of my plot similar to this one (?):

Answer 1

Okay, I found how to resolve the problem... Quite simple:

colorscale = list(c(0, 0.5, 1), c('blue', 'yellow', 'red'))

You can add more intervals (0, 0.2, 0.4...) and change the color string name to rgb or HTML if you want.