Index: src/wp-content/themes/twentynineteen/sass/blocks/_blocks.scss
===================================================================
--- src/wp-content/themes/twentynineteen/sass/blocks/_blocks.scss	(revision 44351)
+++ src/wp-content/themes/twentynineteen/sass/blocks/_blocks.scss	(working copy)
@@ -215,6 +215,9 @@
 		&.is-style-outline .wp-block-button__link:hover {
 			color: white;
 			border-color: $color__background-button-hover;
+			&:not(.has-background) {
+				color: $color__background-button-hover;
+			}
 		}
 	}
 
Index: src/wp-content/themes/twentynineteen/style-rtl.css
===================================================================
--- src/wp-content/themes/twentynineteen/style-rtl.css	(revision 44351)
+++ src/wp-content/themes/twentynineteen/style-rtl.css	(working copy)
@@ -3658,6 +3658,10 @@
   border-color: #111;
 }
 
+.entry .entry-content .wp-block-button.is-style-outline .wp-block-button__link:hover:not(.has-background) {
+  color: #111;
+}
+
 .entry .entry-content .wp-block-archives,
 .entry .entry-content .wp-block-categories,
 .entry .entry-content .wp-block-latest-posts {
Index: src/wp-content/themes/twentynineteen/style.css
===================================================================
--- src/wp-content/themes/twentynineteen/style.css	(revision 44351)
+++ src/wp-content/themes/twentynineteen/style.css	(working copy)
@@ -3670,6 +3670,10 @@
   border-color: #111;
 }
 
+.entry .entry-content .wp-block-button.is-style-outline .wp-block-button__link:hover:not(.has-background) {
+  color: #111;
+}
+
 .entry .entry-content .wp-block-archives,
 .entry .entry-content .wp-block-categories,
 .entry .entry-content .wp-block-latest-posts {