Categories / colors
Creating a Bar Plot with Rainbow-like Gradient Color using Plotly: A Customizable Approach
Creating Custom-Colored Rasters with R: A Step-by-Step Guide
How to Create Gradient Colors in ggplot2: A Step-by-Step Guide for Visualizing Complex Data
Customizing Colors of Points in Quantile-Quantile Plots using qqmath from R's Lattice Package