R igraph: Color Vertices by column content

I am using igraph to plot a graph from SQL Server. I am providing as input a 3 column table:

from   to     color
Node1  NodeA  red
Node1  NodeB  green
Node1  NodeC  blue
Node2  NodeD  red
Node2  NodeE  green

My R script looks like this:

require(igraph)
g <- graph.data.frame(graphdf)
V(g)$label.cex <- 2
png(filename = "'+@outputFile+'", height = 3000, width = 3000, res = 100);
plot(g, vertex.label.family = "sans", vertex.size = 5)
dev.off()

The plot's edges will display with the desired colors, but the vertices themselves do not -- ideally, I want the 'to' vertex to be the color indicated in the 'color' column. I don't care about the 'from's color (it can be the default orange).

I've tried adding this (and variations):

V(g)$color <- graphdf[V(g), 3]

before the png line, but that produces what appear to be random vertex colors.

Copyright Notice：Content Author:「Marc Bernier」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/44573972/r-igraph-color-vertices-by-column-content