change legend labels in "likert" package

library(likert)
data(pisaitems)

##### Item 24: Reading Attitudes
items24 <- pisaitems[,substr(names(pisaitems), 1,5) == 'ST24Q']
head(items24); ncol(items24)

names(items24) <- c(
    ST24Q01="I read only if I have to.",
    ST24Q02="Reading is one of my favorite hobbies.",
    ST24Q03="I like talking about books with other people.",
    ST24Q04="I find it hard to finish books.",
    ST24Q05="I feel happy if I receive a book as a present.",
    ST24Q06="For me, reading is a waste of time.",
    ST24Q07="I enjoy going to a bookstore or a library.",
    ST24Q08="I read only to get information that I need.",
    ST24Q09="I cannot sit still and read for more than a few minutes.",
    ST24Q10="I like to express my opinions about books I have read.",
    ST24Q11="I like to exchange books with my friends.")
str(items24)

l24 <- likert(items24)
l24 #print(l24)
summary(l24)
summary(l24, center=1.5)
summary(l24, center=2)

# xtable
xtable(l24)

##### ----

new_fill_scale <- function(l, labels = letters[seq(l$nlevels)])
{
    opts <- likert.options()
    center <- (l$nlevels - 1)/2 + 1
    lowrange <- 1:floor(center - 0.5)
    highrange <- ceiling(center + 0.5):l$nlevels
    low.color <- "#D8B365"
    neutral.color.ramp <- "white"
    high.color <- "#5AB4AC"
    ramp <- colorRamp(c(low.color, neutral.color.ramp))
    ramp <- rgb(ramp(seq(0, 1, length = length(lowrange) + 
                             1)), maxColorValue = 255)
    bamp <- colorRamp(c(neutral.color.ramp, high.color))
    bamp <- rgb(bamp(seq(0, 1, length = length(highrange) + 
                             1)), maxColorValue = 255)
    cols <- NULL
    if (center%%1 != 0) {
        cols <- c(ramp[1:(length(ramp) - 1)], bamp[2:length(bamp)])
    } else {
        cols <- c(ramp[1:(length(ramp) - 1)], neutral.color, 
                  bamp[2:length(bamp)])
    }
    
    scale_fill_manual(breaks = l$levels, 
                      labels = labels, values = cols, 
                      drop = FALSE)
}

# Plots
plot(l24) + new_fill_scale(l24)
plot(l24) + new_fill_scale(l24, labels = c("lorem", "ipsum", "red", "blue"))