I seem to have done it

cellindex.js

@@ -184,6 +184,53 @@ export const CELL600_METAMAP = {
   581: 67,
   592: 66,
   593: 71,
+
+
+  38: 2,
+  98: 96,
+  120: 34,
+  126: 100,
+  149: 14,
+  156: 20,
+  174: 40,
+  200: 90,
+  210: 102,
+  218: 56,
+  226: 64,
+  252: 44,
+  263: 92,
+  272: 110,
+  279: 38,
+  284: 76,
+  296: 26,
+  311: 98,
+  320: 36,
+  325: 60,
+  334: 52,
+  342: 112,
+  350: 94,
+  362: 104,
+  383: 74,
+  389: 30,
+  400: 42,
+  414: 48,
+  420: 62,
+  438: 108,
+  440: 58,
+  448: 12,
+  458: 24,
+  474: 80,
+  488: 106,
+  494: 16,
+  512: 28,
+  514: 54,
+  530: 22,
+  546: 78,
+  550: 50,
+  558: 32,
+  566: 46,
+  580: 18,
+  600: 10,
 };
 
 export const CELL120_CELL5 = {
@@ -1128,6 +1175,144 @@ export const CELL120_CELL5 = {
 
 };
 
+// my application of Schoute's partition onto one inscribed 600-cell of the
+// 120-cell, which is why this is only 120 out of 600 vertices. This is used
+// to give a coherent colour scheme to the inscribed 5-cells
+
+export const CELL120_CELL5_LABELS {
+  "1": [
+    27,
+    38,
+    140,
+    149,
+    156,
+    165,
+    234,
+    239,
+    241,
+    248,
+    300,
+    301,
+    448,
+    449,
+    458,
+    471,
+    494,
+    499,
+    527,
+    530,
+    573,
+    580,
+    585,
+    600
+  ],
+  "2": [
+    74,
+    87,
+    126,
+    131,
+    185,
+    200,
+    218,
+    223,
+    226,
+    231,
+    313,
+    320,
+    388,
+    389,
+    393,
+    400,
+    427,
+    438,
+    444,
+    453,
+    525,
+    532,
+    543,
+    546
+  ],
+  "3": [
+    258,
+    263,
+    274,
+    279,
+    306,
+    311,
+    356,
+    357,
+    369,
+    376,
+    403,
+    406,
+    413,
+    414,
+    419,
+    420,
+    473,
+    474,
+    487,
+    488,
+    511,
+    512,
+    513,
+    514
+  ],
+  "4": [
+    48,
+    49,
+    105,
+    120,
+    207,
+    210,
+    252,
+    253,
+    284,
+    285,
+    324,
+    325,
+    339,
+    342,
+    347,
+    350,
+    490,
+    503,
+    539,
+    550,
+    558,
+    563,
+    572,
+    581
+  ],
+  "5": [
+    61,
+    68,
+    95,
+    98,
+    174,
+    179,
+    265,
+    272,
+    289,
+    296,
+    331,
+    334,
+    362,
+    367,
+    378,
+    383,
+    425,
+    440,
+    460,
+    469,
+    555,
+    566,
+    592,
+    593
+  ]
+}
+
+
 
 // Schoute's partition via https://arxiv.org/abs/1010.4353
 

label_inscribed_600cell.js

@@ -273,8 +273,110 @@ export function equator(i600, b600, apices) {
 
 export function antipode(shape, nid) {
     const n0 = shape.nodes.filter((n) => n.id === nid)[0];
+    if( !n0 ) {
+        throw new Error(`antipodes error: couldn't find node ${nid} in shape`);
+    }
     const dists = shape.nodes.map((n) => [ dist(n, n0), n ]);
     dists.sort((a, b) => b[0] - a[0]);
-    return dists[0][1].id;
+    return dists[0][1];
 }
 
+
+export function check_antipodes() {
+    const c600 = base_600cell();
+    const seen = {};
+    c600.nodes.map((n) => {
+        const a = antipode(c600, n.id);
+        if( !seen[a.id] && !seen[n.id] ) {
+            seen[a.id] = true;
+            seen[n.id] = true; 
+            console.log(`${n.id} - ${n.label} / ${a.id} - ${a.label}`);
+            if( n.label !== a.label ) {
+                console.lot("MISMATCH");
+            }
+        }
+    });
+}
+
+
+export function meta600_label(b600, iid) {
+    const bid = CELLINDEX.CELL600_METAMAP[iid];
+    const bn = b600.nodes.filter((n) => bid === n.id);
+    return bn[0].label;
+}
+
+
+export function map_antipodes() {
+    const b600 = base_600cell();
+    const i600 = make_one_600cell(); 
+    const already = [];
+    const antimap = {};
+    for( const inid in CELLINDEX.CELL600_METAMAP ) {
+        const bnid = CELLINDEX.CELL600_METAMAP[inid];
+        const banti = antipode(b600, Number(bnid));
+        const ianti = antipode(i600, Number(inid));
+        if( CELLINDEX.CELL600_METAMAP[ianti.id] ) {
+            //console.log(`Anti ${ianti.id} is already mapped`);
+            already.push(ianti.id);
+            const l1 = meta600_label(b600, inid);
+            const l2 = meta600_label(b600, Number(ianti.id));
+            //console.log(`labels: ${l1} ${l2}`);
+        } else {
+            antimap[ianti.id] = banti.id;
+        }
+    }
+    console.log(JSON.stringify(antimap, null, 2));
+}
+
+
+export function check_metamap_completeness() {
+    const b600 = base_600cell();
+    const i600 = make_one_600cell();
+    const labels = {};
+    const bids = {};
+    const mm = CELLINDEX.CELL600_METAMAP;
+    for( const i of i600.nodes ) {
+        if( i.id in mm ) {
+            const ml = meta600_label(b600, i.id);
+            if( !(ml in labels) ) {
+                labels[ml] = [];
+            }
+            labels[ml].push(i.id);
+            bids[mm[i.id]] = 1;
+        } else {
+            console.log(`inscribed node ${i.id} is not in metamap`);
+        }
+    }
+    for( const b of b600.nodes ) {
+        if( !(b.id in bids) ) {
+            console.log(`base mode ${b.id} is not mapped`);
+        }
+    }
+    for ( const label in labels ) {
+        console.log(`label ${label} has ${labels[label].length} nodes`);
+    }
+}
+
+// this gives a mapping from cell-120-ids of one inscribed 600-cell to the
+// metamap labels, which I can then [checks notes] use to colour the 5-cells.
+
+export function metamap_to_labels() {
+    const b600 = base_600cell();
+    const i600 = make_one_600cell();
+    const labels = {
+        1: [],
+        2: [],
+        3: [],
+        4: [],
+        5: [],
+    };
+    for( const inode of i600.nodes ) {
+        const ml = meta600_label(b600, inode.id);
+        labels[ml].push(inode.id);
+    }
+
+    console.log(JSON.stringify(labels, null, 2));
+}
+
+
+metamap_to_labels();