source/blender/draw/engines/gpencil/gpencil_cache_utils.cc

@@ -281,7 +281,7 @@ static float4 grease_pencil_layer_final_tint_and_alpha_get(const GPENCIL_Private
     const float4 onion_col_custom = (use_onion_custom_col) ?
                                         (use_next_col ? float4(color_next, 1.0f) :
                                                         float4(color_prev, 1.0f)) :
-                                        U.gpencil_new_layer_col;
+                                        float4(U.gpencil_new_layer_col);
 
     *r_alpha = use_onion_fade ? (1.0f / abs(onion_id)) : 0.5f;
     *r_alpha *= onion_factor;