Index: src/wp-content/themes/twentyseventeen/assets/css/colors-dark.css
===================================================================
--- src/wp-content/themes/twentyseventeen/assets/css/colors-dark.css	(revision 38966)
+++ src/wp-content/themes/twentyseventeen/assets/css/colors-dark.css	(working copy)
@@ -151,6 +151,23 @@
 	color: #eee;
 }
 
+/* Placeholder text color -- selectors need to be separate to work. */
+.colors-dark ::-webkit-input-placeholder {
+	color: #ddd;
+}
+
+.colors-dark :-moz-placeholder {
+	color: #ddd;
+}
+
+.colors-dark ::-moz-placeholder {
+	color: #ddd;
+}
+
+.colors-dark :-ms-input-placeholder {
+	color: #ddd;
+}
+
 .colors-dark input[type="text"]:focus,
 .colors-dark input[type="email"]:focus,
 .colors-dark input[type="url"]:focus,
Index: src/wp-content/themes/twentyseventeen/style.css
===================================================================
--- src/wp-content/themes/twentyseventeen/style.css	(revision 38966)
+++ src/wp-content/themes/twentyseventeen/style.css	(working copy)
@@ -1042,6 +1042,29 @@
 	background: #bbb;
 }
 
+/* Placeholder text color -- selectors need to be separate to work. */
+::-webkit-input-placeholder {
+	color: #333;
+	font-family: "Libre Franklin", "Helvetica Neue", helvetica, arial, sans-serif;
+}
+
+:-moz-placeholder {
+	color: #333;
+	font-family: "Libre Franklin", "Helvetica Neue", helvetica, arial, sans-serif;
+}
+
+::-moz-placeholder {
+	color: #333;
+	font-family: "Libre Franklin", "Helvetica Neue", helvetica, arial, sans-serif;
+	opacity: 1;
+	/* Since FF19 lowers the opacity of the placeholder by default */
+}
+
+:-ms-input-placeholder {
+	color: #333;
+	font-family: "Libre Franklin", "Helvetica Neue", helvetica, arial, sans-serif;
+}
+
 /*--------------------------------------------------------------
 # Formatting
 --------------------------------------------------------------*/