This is what I threw together, but there's probably a better way to do this; I haven't really used gscatter() for anything before.
% fake data
x = rand(10,1);
y = rand(10,1);
groups = ["bananas"; "blueberries"; "bananas"; "beans"; "beans"; "tomatoes";"blueberries";"bananas";"tomatoes";"tomatoes"];
% label naming info
myLabel = ["tomatoes";"carrots";"blueberries";"beans";"bananas"];
myLabelColor = [0.9 0.0 0.0; 1.0 0.7 0.1; 0.4 0.0 0.8; 0.3 0.7 0.0; 0.9 0.9 0.1];
% gscatter() will list groups based on order of appearance
% figure out which colors are used and the order they're listed
ugroups = unique(groups,'stable');
% then create a new color table ordered to fit the groups as they appear
[islabeled,idx] = ismember(ugroups,myLabel);
if any(~islabeled) % just to avoid confusion
error('grouping variable contains groups which have no assigned label');
end
CT = myLabelColor(idx,:);
% plot it
hs = gscatter(x,y,groups,CT);
