diff --git a/R/bs-theme-preset-builtin.R b/R/bs-theme-preset-builtin.R
index dc2cda74b..b20bf282f 100644
--- a/R/bs-theme-preset-builtin.R
+++ b/R/bs-theme-preset-builtin.R
@@ -22,19 +22,22 @@ builtin_bundle <- function(name = "shiny", version = version_default()) {
     )
   }
 
-  path_variables <- path_builtin_theme(name, "_variables.scss", version = version)
-  path_rules <- path_builtin_theme(name, "_rules.scss", version = version)
+  sass_parts <- rlang::set_names(c("variables", "mixins", "rules"))
+
+  sass_files <- lapply(sass_parts, function(part) {
+    path <- path_builtin_theme(name, paste0("_", part, ".scss"), version = version)
+    if (file.exists(path)) sass_file(path)
+  })
 
   sass_bundle(
     "builtin" = sass_layer(
       file_attachments = attachments,
       defaults = list(
         '$web-font-path: "font.css" !default;',
-        sass_file(path_variables)
+        sass_files$variables
       ),
-      rules = list(
-        if (file.exists(path_rules)) sass_file(path_rules)
-      )
+      mixins = list(sass_files$mixins),
+      rules = list(sass_files$rules)
     )
   )
 }
diff --git a/inst/builtin/bs5/shiny/_mixins.scss b/inst/builtin/bs5/shiny/_mixins.scss
new file mode 100644
index 000000000..305a69b6e
--- /dev/null
+++ b/inst/builtin/bs5/shiny/_mixins.scss
@@ -0,0 +1,3 @@
+// Shiny: selectInput() and selectizeInput()
+$selectize-color-dropdown-item-active: $component-active-bg !default;
+$selectize-color-dropdown-item-active-text: $component-active-color !default;
diff --git a/inst/builtin/bs5/shiny/_rules.scss b/inst/builtin/bs5/shiny/_rules.scss
index 7d34f4ee9..729d342df 100644
--- a/inst/builtin/bs5/shiny/_rules.scss
+++ b/inst/builtin/bs5/shiny/_rules.scss
@@ -5,17 +5,11 @@ $web-font-path: "https://fonts.googleapis.com/css2?family=Open+Sans:ital,wght@0,
 }
 
 // move checkbox and radio text slightly to the right
-.checkbox input,
-.radio input {
-  margin-right: 0.35em;
-}
-
-// make selected item more accessible
-.selectize-dropdown-content .option.selected.active,
-.selectize-dropdown-content .option:hover,
-.selectize-dropdown-content .option:active {
-  background-color: $blue;
-  color: $white;
+.checkbox,
+.radio {
+  input {
+    margin-right: 0.35em;
+  }
 }
 
 // make non-selected items slightly different visually (but still 3:1 contrast)
diff --git a/inst/builtin/bs5/shiny/_variables.scss b/inst/builtin/bs5/shiny/_variables.scss
index b8da7bfd1..8d8f2ea85 100644
--- a/inst/builtin/bs5/shiny/_variables.scss
+++ b/inst/builtin/bs5/shiny/_variables.scss
@@ -23,14 +23,14 @@ $gray-700: #48505f !default;
 $gray-800: #343a46 !default;
 $gray-900: #1d1f21 !default;
 
-$default: #dee2e6 !default;
-$primary: #007bc2 !default;
+$default: $gray-300 !default;
+$primary: $blue !default;
 $secondary: #404040 !default;
-$success: #00891a !default;
-$info: #03c7e8 !default;
-$warning: #f9b928 !default;
-$danger: #c10000 !default;
-$light: #f8f8f8 !default;
+$success: $green !default;
+$info: $cyan !default;
+$warning: $yellow !default;
+$danger: $red !default;
+$light: $gray-100 !default;
 $dark: #202020 !default;
 
 $default-rgb: 222, 226, 230 !default;
@@ -53,10 +53,12 @@ $gradient: linear-gradient(
   rgba(255, 255, 255, 0)
 ) !default;
 
-$base-font: "Open Sans" !default;
-$font-family-sans-serif: $base-font, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif !default;
+$body-color: $gray-900 !default;
+$body-bg: $white !default;
+
+// Fonts
+$font-family-base: "Open Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif !default;
 $font-family-monospace: "Source Code Pro", SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace	!default;
-$headings-font-family: $font-family-sans-serif !default;
 
 $root-font-size: 18px !default;
 $body-font-size: 1rem !default;
@@ -65,23 +67,21 @@ $h1-font-size: 2.1rem !default;
 $body-font-weight: 400 !default;
 $headings-font-weight: 400 !default;
 
-$body-color: $gray-900 !default;
-$body-bg: #ffffff !default;
-
+// Spacing
 $hr-margin-y: 2rem !default;
 
+// Buttons
 $input-btn-font-size: 15px !default;
-
 $btn-font-weight: 500 !default;
 $btn-padding-y: 0.75em !default;
 $btn-padding-x: 2em !default;
 
-
+// Form controls
 $form-check-input-width: 1.2em !default;
 $form-check-input-border-radius: 2px !default;
 $form-check-margin-bottom: 0.25rem !default;
 $form-text-color: $red !default;
 
+// Borders
 $input-border-color: $gray-500 !default;
-
 $border-radius: 3px !default;