diff --git a/app/assets/javascripts/repositories/stock.js b/app/assets/javascripts/repositories/stock.js
index 30efdd7ad..4e08ba0b6 100644
--- a/app/assets/javascripts/repositories/stock.js
+++ b/app/assets/javascripts/repositories/stock.js
@@ -4,8 +4,8 @@ var RepositoryStockValues = (function() {
   const UNIT_SELECTOR = '#repository-stock-value-units';
 
   function formatDecimalValue(value, decimals) {
-    let regexp = decimals === 0 ? /[^0-9]/g : /[^0-9.]/g;
-    return value.replace(regexp, '').match(new RegExp(`^\\d*(\\.\\d{0,${decimals}})?`))[0];
+    let regexp = decimals === 0 ? /[^-0-9]/g : /[^-0-9.]/g;
+    return value.replace(regexp, '').match(new RegExp(`^-?\\d*(\\.\\d{0,${decimals}})?`))[0];
   }
 
   function updateChangeAmount($element) {
@@ -36,6 +36,7 @@ var RepositoryStockValues = (function() {
     $('#change_amount').val(inputAmount);
 
     $('#repository_stock_value_amount').val(newAmount);
+    $('.stock-final-container').toggleClass('negative', newAmount < 0);
     $('.stock-final-container .value').text(
       formatDecimalValue(String(newAmount), $('#stock-input-amount').data('decimals'))
     );
diff --git a/app/assets/stylesheets/repository/stock_modal.scss b/app/assets/stylesheets/repository/stock_modal.scss
index 1970db839..c20cd68b1 100644
--- a/app/assets/stylesheets/repository/stock_modal.scss
+++ b/app/assets/stylesheets/repository/stock_modal.scss
@@ -32,6 +32,12 @@
         @include font-small;
       }
 
+      &.negative {
+        .value {
+          color: $brand-danger;
+        }
+      }
+
       &.error {
         .value {
           color: $brand-danger;
diff --git a/app/views/repository_stock_values/_manage_modal_content.html.erb b/app/views/repository_stock_values/_manage_modal_content.html.erb
index 8d4d0da24..ea9357d92 100644
--- a/app/views/repository_stock_values/_manage_modal_content.html.erb
+++ b/app/views/repository_stock_values/_manage_modal_content.html.erb
@@ -114,7 +114,7 @@
       <div class="row">
         <div class="col-sm-12">
           <div class="stock-update-view">
-            <div class="stock-initial-container">
+            <div class="stock-initial-container <%= 'negative' if repository_stock_value.amount.negative? %>">
               <span class="subtitle"><%= t('repository_stock_values.manage_modal.current_stock') %></span>
               <span class="value"><%= repository_stock_value.formatted_value %></span>
               <span class="units"><%= repository_stock_value.repository_stock_unit_item&.data %></span>
@@ -122,7 +122,7 @@
             <div class="stock-arrow">
               <i class="fas fa-arrow-right"></i>
             </div>
-            <div class="stock-final-container">
+            <div class="stock-final-container <%= 'negative' if repository_stock_value.amount.negative? %> ">
               <span class="subtitle"><%= t('repository_stock_values.manage_modal.new_stock') %></span>
               <span class="value"><%= repository_stock_value.formatted_value %></span>
               <span class="units"><%= repository_stock_value.repository_stock_unit_item&.data %></span>