src/_core/components/thumbnail/_variables/_variables.scss
@import '../../../variables'; // base colors
//== Thumbnails
//
//##
//** Padding around the thumbnail image
$thumbnail-padding: 4px !default;
//** Thumbnail background color
$thumbnail-bg: $body-bg !default;
//** Thumbnail border color
$thumbnail-border: #ddd !default;
//** Thumbnail border radius
$thumbnail-border-radius: $border-radius-base !default;
//** Custom text color for thumbnail captions
$thumbnail-caption-color: $text-color !default;
//** Padding around the thumbnail caption
$thumbnail-caption-padding: 9px !default;