Fix colorsTexture size (#29061)

src/objects/BatchedMesh.js

@@ -206,7 +206,7 @@ class BatchedMesh extends Mesh {
 
 	_initColorsTexture() {
 
-		let size = Math.sqrt( this._maxIndexCount );
+		let size = Math.sqrt( this._maxInstanceCount );
 		size = Math.ceil( size );
 
 		// 4 floats per RGBA pixel initialized to white