diff --git a/package-lock.json b/package-lock.json
index 7e6b89a..9051999 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,9 +9,9 @@
         "@resvg/resvg-js": "^2.6.2",
         "d3": "^7.9.0",
         "d3-color": "^3.1.0",
+        "d3-color-difference": "^0.1.3",
         "d3-dsv": "^3.0.1",
         "d3-time-format": "^4.1.0",
-        "hex-color-to-color-name": "^1.0.2",
         "jsdom": "^26.0.0",
         "lodash.shuffle": "^4.2.0",
         "random": "^5.1.1",
@@ -1766,6 +1766,19 @@
         "node": ">=12"
       }
     },
+    "node_modules/d3-color-difference": {
+      "version": "0.1.3",
+      "resolved": "https://registry.npmjs.org/d3-color-difference/-/d3-color-difference-0.1.3.tgz",
+      "integrity": "sha512-yAGiVdTZR/wpI66n85xvkTvjxFth0IuGrEeX/anl1Q5rzNc2/V7oOjoJdqQnahOuS+SgbAR0zu8T0SYY7hGTtw==",
+      "dependencies": {
+        "d3-color": "^1.1.0"
+      }
+    },
+    "node_modules/d3-color-difference/node_modules/d3-color": {
+      "version": "1.4.1",
+      "resolved": "https://registry.npmjs.org/d3-color/-/d3-color-1.4.1.tgz",
+      "integrity": "sha512-p2sTHSLCJI2QKunbGb7ocOh7DgTAn8IrLx21QRc/BSnodXM4sv6aLQlnfpvehFMLZEfBc6g9pH9SWQccFYfJ9Q=="
+    },
     "node_modules/d3-contour": {
       "version": "4.0.2",
       "resolved": "https://registry.npmjs.org/d3-contour/-/d3-contour-4.0.2.tgz",
@@ -2482,11 +2495,6 @@
         "he": "bin/he"
       }
     },
-    "node_modules/hex-color-to-color-name": {
-      "version": "1.0.2",
-      "resolved": "https://registry.npmjs.org/hex-color-to-color-name/-/hex-color-to-color-name-1.0.2.tgz",
-      "integrity": "sha512-YKPBFTSbYIHH8YKcJB4Q5PV+Tr+kvDXpV60BcPMUu5CSZUcc/qOOx7lkr7luk6MSXKd5A82yfPGZTgedIdQ+aA=="
-    },
     "node_modules/highlight.js": {
       "version": "11.11.1",
       "resolved": "https://registry.npmjs.org/highlight.js/-/highlight.js-11.11.1.tgz",
diff --git a/package.json b/package.json
index 58600cf..3fb1144 100644
--- a/package.json
+++ b/package.json
@@ -13,9 +13,9 @@
     "@resvg/resvg-js": "^2.6.2",
     "d3": "^7.9.0",
     "d3-color": "^3.1.0",
+    "d3-color-difference": "^0.1.3",
     "d3-dsv": "^3.0.1",
     "d3-time-format": "^4.1.0",
-    "hex-color-to-color-name": "^1.0.2",
     "jsdom": "^26.0.0",
     "lodash.shuffle": "^4.2.0",
     "random": "^5.1.1",
diff --git a/poptimal.js b/poptimal.js
index 187517c..a98fcf1 100644
--- a/poptimal.js
+++ b/poptimal.js
@@ -12,9 +12,7 @@ const xlinkns = "http://www.w3.org/1999/xlink";
 const svgns = "http://www.w3.org/2000/svg";
 
 import {RADIUS_OPTS, DotMaker} from './src/components/dots.js';
-import {PALETTES} from './src/components/palettes.js';
-
-import { GetColorName } from "hex-color-to-color-name";
+import {PALETTES, colour_to_text} from './src/components/palettes.js';
 
 const CELL = 10;
 const MAG = 2;
@@ -40,12 +38,6 @@ function randomise_params() {
 	}
 }
 
-function colour_to_text(d3color) {
-	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);
@@ -138,6 +130,13 @@ async function main() {
 		.default('s', 1200)
 		.default('c', 'config.json').argv;
 
+	if( argv.t ) {
+		const blue = d3.rgb(0, 0, 255);
+		const name = await colour_to_text(blue, "./rgb.txt");
+		console.log(name);
+		process.exit();
+	}
+
 	const cfjson = await promises.readFile(argv.c);
   	const cf = JSON.parse(cfjson);
 
diff --git a/src/components/palettes.js b/src/components/palettes.js
index 7d01ac5..3b0db99 100644
--- a/src/components/palettes.js
+++ b/src/components/palettes.js
@@ -2,6 +2,9 @@
 import * as d3 from "d3-color";
 import shuffle from "lodash.shuffle";
 import random from "random";
+import { promises } from "fs";
+
+import * as d3cd from "d3-color-difference";
 
 const PALETTES = new Map([
 	[ "random RGB", palette_random ], 
@@ -75,4 +78,33 @@ function palette_cmy() {
 	return shuffle(cols);
 }
 
-export { PALETTES }
+async function parse_colours(colourfile) {
+	const colourBuff = await promises.readFile(colourfile);
+	const colours = colourBuff.toString();
+	const colmap = new Map();
+	const seen = new Set(); 
+	colours.split(/\n/).map((l) => {
+		const m = l.match(/(\d+)\s+(\d+)\s+(\d+)\s+(.*)/);
+		if( m ) {
+			const sig = `${m[1]},${m[2]},${m[3]}`;
+			if( !seen.has(sig) ) {
+				colmap.set(m[4], d3.rgb(m[1], m[2], m[3]));
+				seen.add(sig);
+			}
+		}
+	});
+	return colmap;
+}
+
+async function colour_to_text(d3color, colourfile) {
+	const colours = await parse_colours(colourfile);
+	const diffs = []
+	for( const [ name, colour] of colours) {
+		diffs.push({name: name, dist: d3cd.differenceCie76(colour, d3color)});
+	}
+	diffs.sort((a, b) => a.dist - b.dist);
+	return diffs[0].name;
+} 
+
+
+export { PALETTES, colour_to_text }