Below scss will help you to create rgba of all Bootstrap colors (and theme colors). Example : bg-light-rgba-1, text-dark-rgba-8, bg-primary-rgba-3, text-purple-rgba-5

_bootstrap-rgba-colors.scss

// this will generate rgba colors from bootstrap colors and theme-colors
// examples : bg-light-rgba-1, text-dark-rgba-8, bg-primary-rgba-3, text-purple-rgba-5
// please ensure to import ~bootstrap/scss/bootstrap.scss before this file
$all-colors: map-merge($map1: $colors, $map2: $theme-colors);
$transparencies: (1:0.1, 2: 0.2, 3: 0.3, 4: 0.4, 5: 0.5, 6: 0.6, 7: 0.7, 8: 0.8, 9: 0.9);
@each $color in map-keys($all-colors) {
    @each $alpha,
    $opacity in $transparencies {
      @each $prop, $abbrev in (background-color: bg, color: text){
        .#{$abbrev}-#{$color}-rgba-#{$alpha} {
            $main-color: map-get($map: $all-colors, $key: $color);
            #{$prop}: rgba($main-color, $opacity) !important;
        }
      }
    }
}