Highlight specific histogram bars in a shiny app

Question

I have the dataframe below:

x1<-floor(runif(100, 1,5))
x2<-floor(runif(100, 6,10))
x3<-floor(runif(100, 10,14))
x4<-floor(runif(100, 15,19))
result<-floor(runif(100,100,110))
df<-data.frame(x1,x2,x3,x4,result)

x1 x2 x3 x4 result
1  4  6 11 15    101
2  1  6 12 18    108
3  2  6 13 15    103
4  3  7 13 17    107
5  2  8 10 18    108
6  2  9 12 16    105

and I have a created a shiny app with 4 sliders one for every x value and a histogram which displays the frequency of result. What I want to do is highlight with a different color than the darkblue the values of result based on the combination of the x values. If for example I select 4,6,11,15 (first line of the df) then the 101 bar should be highlighted. If I select one value from every line of the first 4 then 101,108,103,107 should be highlighted with the same color which should be different from darkblue.

#ui.r
library(shiny)
library(shinyWidgets)
library(ggplot2)
pageWithSidebar(
  headerPanel("Histogram"),
  sidebarPanel(width=2,
               h4("Blood-center specific variables"),
               sliderTextInput(
                 inputId = "col", label = "Annual number of collections", 
                 choices = sort(unique(df$x1),decreasing = F), selected = min(df$x1), 
                 grid = TRUE
               ),
               sliderTextInput(
                 inputId = "rat", label = "Collection: import ratio ", 
                 choices = sort(unique(df$x2),decreasing = F), selected = min(df$x2), 
                 grid = TRUE
               ),
               sliderTextInput(
                 inputId = "aph", label = "Apheresis: WB ratio", 
                 choices = sort(unique(df$x3),decreasing = F), selected = min(df$x3), 
                 grid = TRUE
               ),
               sliderTextInput(
                 inputId = "tra", label = "Current trauma distribution %", 
                 choices = sort(unique(df$x4),decreasing = F), selected = min(df$x4), 
                 grid = TRUE
               )


  ),
  mainPanel(
    fluidRow(
      plotOutput("h1")
    )

  )
)
#server.r
library(shiny)
library(shinyWidgets)
library(ggplot2)
function(input, output) {

  output$h1<-renderPlot(
    ggplot(df, aes(x=result))+
      geom_histogram(color="darkblue", fill="lightblue")
  )

}