Help with effective data structure, to represent CIE Lab ab diagram

I'm at a point where I'm making progress on my project even though I'm surely not approaching it from an efficient coding perspective, not taking advantage of the modeling efficiency that linear algebra offers? But, here goes. As can be seen from my code and the screen capture, I'm trying to create a CIE Lab 'ab' diagram. This is my humble code :

clc

global ax;

fig=figure('Position', [600 300 1000 1000]);

ax = axes(fig);

axis([-128 128 -128 128]);

xticks([-128 -112 -96 -80 -64 -48 -32 -16 0 16 32 48 64 80 96 112 128]);

yticks([-128 -112 -96 -80 -64 -48 -32 -16 0 16 32 48 64 80 96 112 128]);

grid on;

grid minor;

hold on;

OffsetX=-96;

OffsetY=0;

Axe_A = transpose(linspace(-96, 96, 49));

Axe_L = transpose(linspace(50, 50, 49));

Axe_B = transpose(linspace(0, 0, 49));

InGamut = transpose(linspace(0, 0, 49));

Lab = [Axe_L, Axe_A, Axe_B];

RGB = lab2rgb(Lab);

%Add 4th column to flag out of gamut colors

RGBx = [RGB InGamut];

[row,col] = size(RGB);

for ROW = 1:row

if RGB(ROW,1) < 0

RGBx(ROW,1) = 0;

RGBx(ROW,4) = 1;

end

if RGB(ROW,1) > 1

RGBx(ROW,1) = 1;

RGBx(ROW,4) = 1;

end

if RGB(ROW,2) < 0

RGBx(ROW,2) = 0;

RGBx(ROW,4) = 1;

end

if RGB(ROW,2) > 1

RGBx(ROW,2) = 1;

RGBx(ROW,4) = 1;

end

if RGB(ROW,3) < 0

RGBx(ROW,3) = 0;

RGBx(ROW,4) = 1;

end

if RGB(ROW,3) > 1

RGBx(ROW,3) = 1;

RGBx(ROW,4) = 1;

end

end

T = RGBx;

OffsetX=-96;

OffsetY=0;

for ROW = 1:row

if RGBx(ROW,4) == 0

rectangle(ax,'Position',[OffsetX OffsetY 4 4],'FaceColor',[RGBx(ROW,1) RGBx(ROW,2) RGBx(ROW,3)], 'LineStyle', 'none');

else

rectangle(ax,'Position',[OffsetX OffsetY 4 4],'FaceColor',[RGBx(ROW,1) RGBx(ROW,2) RGBx(ROW,3)]');

end

OffsetX=OffsetX+4;

end

hold on;

FirstLine = [-128, -112, -96, -80, -64, -48, -32, -16, 0, 16, 32, 48, 64, 80, 96, 112, 128];

array = zeros(17, 17);

for k = 1:17

array(k,:) = FirstLine;

end

for m= 1:17

for k = 1:17

scatter(array(1,m), array(1,k));

end

end

alpha(.5)

And this is the result :

As far as plotting the Lab values, at the constant L* = 50 value, I use a 'tile' size of 4x4. (Later, when I'm satisfied, I'll expand this to 1x1 or 2x2). As you can see from the screen capture, I only have one row worth of data.

The stumbling block I'm hitting is I don't know how best to represent the entire Lab values, from -128 to 128, in a* and b* under, possibly, one data structure?

I sense that, I could possibly expand the following line :

Lab = [Axe_L, Axe_A, Axe_B];

... into a Lab(49) array, which would be a monster array of 49 'outer rows' each containing 49 columns of a* and b* sub-arrays? And that's where I'm kind of stuck because I'm not sure this makes any kind of programming sense. I've been thinking about how best to approach this for a while now and I'm probably at the stage of asking for suggestions...

BTW, I intend to reduce the opacity of the 'circles' close to 0 so that they're not materially changing the underlying rectangle colors while giving me the benefit of data tips.

Before taking my whole current approach, I toyed with the idea of using a colormap, to hold the Lab2rgb values but I'm not sure that was the best approach.

Thank you in advance for your kind help and patience.

I noticed I'm using loops that considerably slow down the script execution but I'm not really concerned about speed.