如何填充整个单元格背景在列标题kableExtra当针织到PDF

我正在用R Markdown中的kableExtra包将表格编织成PDF，我想知道是否有人有解决方案来确保列标题(黑色)、列组标题(黑色)和填充行(红色)的背景 colored颜色 填充整个单元格.如下图所示，各个单元格只填充了部分内容，这看起来有点傻.

Example code:个

---
title: "Test Doc"
output: pdf_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(
  echo = FALSE,
  message = FALSE,
  warning = FALSE,
  dev = "cairo_pdf"
  )
```

```{r}
library(tidyverse)
library(kableExtra)
```

```{r}
set.seed(1)

df <- data.frame(
  id = LETTERS[1:10],
  var1 = rnorm(10, 50, 10),
  var2 = rnorm(10, 50, 10),
  var3 = rnorm(10, 50, 10),
  var4 = rnorm(10, 50, 10),
  var5 = rnorm(10, 50, 10),
  var6 = rnorm(10, 50, 10),
  grp = rep(paste("Group", 1:2), each = 5)
)
```

```{r}
kbl(df[1:7],
    booktabs = TRUE,
    escape = FALSE,
    align = c("l", rep("c", ncol(df) - 1))) %>%
  kable_styling(latex_options = c("HOLD_position"),
                font_size = 8) %>%
  add_header_above(c(" " = 1, "colgroup1" = 3, "colgroup2" = 3), background = "black",
                     color = "white", bold = TRUE) %>%
  row_spec(row = 0, background = "black", color = "white", bold = TRUE) %>%
  pack_rows(index = table(fct_inorder(df$grp)), background = "#ED1B2F",
            color = "white", bold = TRUE, extra_latex_after = "\\midrule{}")
```