Overlay gray ROI on an image

Based on this question (https://www.mathworks.com/matlabcentral/answers/1620785-overlay-roi-on-an-image) and one of the answers (@Image Analyst), I can not overlay the grayRoi on the rgbImage as the outcome image as some colors where it should be gray. How can I solve it?

Code:

close all;
clear all;
clc;
rgbImage = imread('sevilla.jpg');
figure('Name','Sevilla');
imshow(rgbImage)
axis('on', 'image')
uiwait(helpdlg('Draw a rectangle'))
roi = drawrectangle('StripeColor','r')
pos = roi.Position
% OPTIONAL Get rid of graphical overlay and replace with yellow rectangle.
delete(roi)
rectangle('Position', pos, 'EdgeColor', 'y', 'LineWidth', 2);
% Crop image using indexing.
col1 = floor(pos(1)); % Column 1
col2 = ceil(pos(1) + pos(3)); % Column 2
row1 = floor(pos(2)); % Row 1
row2 = ceil(pos(2) + pos(4));    % Row 2
GrayRoi = rgb2gray(rgbImage(row1 : row2, col1 : col2, :));
figure
imshow(GrayRoi)
axis('on', 'image')

newI = rgbImage;
newI(row1 : row2, col1 : col2) = GrayRoi;
figure
imshow(newI)

Answer 1

[Walter Roberson]

newI(row1 : row2, col1 : col2) = repmat(GrayRoi, [1 1 size(newI,3)]);

[Ely Raz]

Thanks for the reply but I get this error:

Unable to perform assignment because the size of the left side is 164-by-140 and the size of the right side is 164-by-140-by-3.

Error in mergeGrayCrop (line 25)
newI(row1 : row2, col1 : col2) = repmat(GrayRoi, [1 1 size(newI,3)]);

[Walter Roberson]

newI(row1 : row2, col1 : col2, :) = repmat(GrayRoi, [1 1 size(newI,3)]);