diff --git a/optuna/visualization/_rank.py b/optuna/visualization/_rank.py
index 0ec4028a10..ead722555c 100644
--- a/optuna/visualization/_rank.py
+++ b/optuna/visualization/_rank.py
@@ -211,22 +211,20 @@ def _get_rank_subplot_info(
     yaxis = _get_axis_info(trials, y_param)
 
     infeasible_trial_ids = []
-    for i in range(len(trials)):
-        constraints = trials[i].system_attrs.get(_CONSTRAINTS_KEY)
+    filtered_ids = []
+    for idx, trial in enumerate(trials):
+        constraints = trial.system_attrs.get(_CONSTRAINTS_KEY)
         if constraints is not None and any([x > 0.0 for x in constraints]):
-            infeasible_trial_ids.append(i)
+            infeasible_trial_ids.append(idx)
+        if x_param in trial.params and y_param in trial.params:
+            filtered_ids.append(idx)
 
-    colors[infeasible_trial_ids] = (204, 204, 204)  # equal to "#CCCCCC"
-
-    filtered_ids = [
-        i
-        for i in range(len(trials))
-        if x_param in trials[i].params and y_param in trials[i].params
-    ]
     filtered_trials = [trials[i] for i in filtered_ids]
     xs = [trial.params[x_param] for trial in filtered_trials]
     ys = [trial.params[y_param] for trial in filtered_trials]
     zs = target_values[filtered_ids]
+
+    colors[infeasible_trial_ids] = (204, 204, 204)
     colors = colors[filtered_ids]
     return _RankSubplotInfo(
         xaxis=xaxis,