SASS/SCSS：Bootstrap5颜色功能运行不正常？

您需要将$min-contrast-ratio变量的值更改为较低的值。

默认情况下，Bootstrap v5 将4.5默认值设置为推荐的 WCAG [ISO-9241-3] 和 [ANSI-HFES-100-1988]，特别是对于老年人或视力下降的人。
https://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html

在您的情况下，请将对比度更改为较低的值，但请注意视力不佳或认知障碍的用户可能无法阅读您的文本。

添加$min-contrast-ratio: 2.5;到您的代码将覆盖默认设置，使您的代码中的文本变为白色。

// Variables
$min-contrast-ratio: 2.5;

// Bootstrap
$_luminance-list: .0008 .001 .0011 .0013 .0015 .0017 .002 .0022 .0025 .0027 .003 .0033 .0037 .004 .0044 .0048 .0052 .0056 .006 .0065 .007 .0075 .008 .0086 .0091 .0097 .0103 .011 .0116 .0123 .013 .0137 .0144 .0152 .016 .0168 .0176 .0185 .0194 .0203 .0212 .0222 .0232 .0242 .0252 .0262 .0273 .0284 .0296 .0307 .0319 .0331 .0343 .0356 .0369 .0382 .0395 .0409 .0423 .0437 .0452 .0467 .0482 .0497 .0513 .0529 .0545 .0561 .0578 .0595 .0612 .063 .0648 .0666 .0685 .0704 .0723 .0742 .0762 .0782 .0802 .0823 .0844 .0865 .0887 .0908 .0931 .0953 .0976 .0999 .1022 .1046 .107 .1095 .1119 .1144 .117 .1195 .1221 .1248 .1274 .1301 .1329 .1356 .1384 .1413 .1441 .147 .15 .1529 .1559 .159 .162 .1651 .1683 .1714 .1746 .1779 .1812 .1845 .1878 .1912 .1946 .1981 .2016 .2051 .2086 .2122 .2159 .2195 .2232 .227 .2307 .2346 .2384 .2423 .2462 .2502 .2542 .2582 .2623 .2664 .2705 .2747 .2789 .2831 .2874 .2918 .2961 .3005 .305 .3095 .314 .3185 .3231 .3278 .3325 .3372 .3419 .3467 .3515 .3564 .3613 .3663 .3712 .3763 .3813 .3864 .3916 .3968 .402 .4072 .4125 .4179 .4233 .4287 .4342 .4397 .4452 .4508 .4564 .4621 .4678 .4735 .4793 .4851 .491 .4969 .5029 .5089 .5149 .521 .5271 .5333 .5395 .5457 .552 .5583 .5647 .5711 .5776 .5841 .5906 .5972 .6038 .6105 .6172 .624 .6308 .6376 .6445 .6514 .6584 .6654 .6724 .6795 .6867 .6939 .7011 .7084 .7157 .7231 .7305 .7379 .7454 .7529 .7605 .7682 .7758 .7835 .7913 .7991 .807 .8148 .8228 .8308 .8388 .8469 .855 .8632 .8714 .8796 .8879 .8963 .9047 .9131 .9216 .9301 .9387 .9473 .956 .9647 .9734 .9823 .9911 1;

@function color-contrast($background, $color-contrast-dark: $color-contrast-dark, $color-contrast-light: $color-contrast-light, $min-contrast-ratio: $min-contrast-ratio) {
  $foregrounds: $color-contrast-light, $color-contrast-dark, $white, $black;
  $max-ratio: 0;
  $max-ratio-color: null;

  @each $color in $foregrounds {
    $contrast-ratio: contrast-ratio($background, $color);
    @if $contrast-ratio > $min-contrast-ratio {
      @return $color;
    } @else if $contrast-ratio > $max-ratio {
      $max-ratio: $contrast-ratio;
      $max-ratio-color: $color;
    }
  }

  @warn "Found no color leading to #{$min-contrast-ratio}:1 contrast ratio against #{$background}...";

  @return $max-ratio-color;
}

@function contrast-ratio($background, $foreground: $color-contrast-light) {
  $l1: luminance($background);
  $l2: luminance(opaque($background, $foreground));

  @return if($l1 > $l2, ($l1 + .05) / ($l2 + .05), ($l2 + .05) / ($l1 + .05));
}

@function luminance($color) {
  $rgb: (
    "r": red($color),
    "g": green($color),
    "b": blue($color)
  );

  @each $name, $value in $rgb {
    $value: if($value / 255 < .03928, $value / 255 / 12.92, nth($_luminance-list, $value + 1));
    $rgb: map-merge($rgb, ($name: $value));
  }

  @return (map-get($rgb, "r") * .2126) + (map-get($rgb, "g") * .7152) + (map-get($rgb, "b") * .0722);
}

@function opaque($background, $foreground) {
  @return mix(rgba($foreground, 1), $background, opacity($foreground) * 100);
}

@function tint-color($color, $weight) {
  @return mix(white, $color, $weight);
}

@function shade-color($color, $weight) {
  @return mix(black, $color, $weight);
}

@function shift-color($color, $weight) {
  @return if($weight > 0, shade-color($color, $weight), tint-color($color, -$weight));
}

$white:          #ffffff       !default;
$black:          #000000       !default;

$min-contrast-ratio:   4.5                   !default;
$color-contrast-dark:  $black                !default;
$color-contrast-light: $white                !default;

$orange: #fd7e14 !default;

$orange-50:  tint-color($orange, 90%)  !default;
$orange-100: tint-color($orange, 70%)  !default;
$orange-200: tint-color($orange, 50%)  !default;
$orange-300: tint-color($orange, 30%)  !default;
$orange-400: tint-color($orange, 10%)  !default;
$orange-500: $orange                   !default;
$orange-600: shade-color($orange, 20%) !default;
$orange-700: shade-color($orange, 40%) !default;
$orange-800: shade-color($orange, 60%) !default;
$orange-900: shade-color($orange, 80%) !default;

$theme-colors: () !default;
$theme-colors: map-merge(
    (
        "orange":   $orange
    ),
    $theme-colors
);

@mixin alert-variant(
  $background,
  $border,
  $color: color-contrast($background)
) {
  color: $color;
  background-color: $background;
  border-color: $border;
}

@each $color, $value in $theme-colors {
  .alert-#{$color} {
    @include alert-variant($value, $value);
    padding: 15px 10px;
    font-size: 1rem;
    text-align: center;
    margin-bottom: 15px;
  }
}

或者，color-contrast如果您不想直接或全局影响最小对比度，您可以向函数添加额外的参数。

@mixin alert-variant(
  $background,
  $border,
  $color: color-contrast(
        $background,
        $color-contrast-dark, // Black text
        $color-contrast-light, // White text
        2.5 // minimum contrast ratio
  )
) {
  color: $color;
  background-color: $background;
  border-color: $border;
}