Red coins should not be merged.
MODIFY
WalletWasabi/Models/ChaumianCoinJoin/CcjClientState.cs
WalletWasabi/Models/ChaumianCoinJoin/CcjClientState.cs
@@ -275,7 +275,8 @@ namespace WalletWasabi.Models.ChaumianCoinJoin
int bestMinAnonset = bestSet.Min(x => x.AnonymitySet);
var bestSum = Money.Satoshis(bestSet.Sum(x => x.Amount));
- if (!bestSum.Almost(amountNeeded, Money.Coins(0.0001m)))
+ if (!bestSum.Almost(amountNeeded, Money.Coins(0.0001m)) // Otherwise it wouldn't generate change so consolidation would make no sense.
+ && bestMinAnonset > 1) // Red coins should never be merged.
{
IEnumerable<SmartCoin> coinsThoseCanBeConsolidated = coins
.Except(bestSet) // Get all the registrable coins, except the already chosen ones.

Red coins should not be merged.