diff --git a/poptimal.js b/poptimal.js
index fea8922..f7aa5a5 100644
--- a/poptimal.js
+++ b/poptimal.js
@@ -41,13 +41,17 @@ function randomise_params() {
 }
 
 function colour_to_text(d3color) {
-	return GetColorName(d3color.formatHex()).toLowerCase();
+	const rawname = GetColorName(d3color.formatHex()).toLowerCase();
+	// some return values are things like "cyan / aqua": take the first
+	const parts = rawname.split(/\//);
+	return parts[0].trim();
 } 
 
 function image_description(params) {
 	const bgc = colour_to_text(params.background);
 	const dotc = params.patterns.map((p) => colour_to_text(p.colour));
-	return `A pattern of ${dotc[0]} and ${dotc[1]} dots on a ${bgc} background`;
+	const a = bgc.match(/^[aeiou]/) ? 'an' : 'a';
+	return `A pattern of ${dotc[0]} and ${dotc[1]} dots on ${a} ${bgc} background`;
 
 }