HI,
this was my final solution.
colormap = jet; % or type out values of jet into colormap
x = 1:0.1:20; % dummy dataset
y = sin(x);
newrange = [1:64/100:64]'; % temperature range of -25degC to +75degC = 100 points
oldrange = [1:1:64]';
colormapinterp = interp1(oldrange,colormap,newrange); %Vq = interp1(X,V,Xq);
temprange = [-25:1:75];
temp1 = -15;
temp2 = 25;
temp3 = 65;
k1 = find(temprange==temp1); % find index of each temperature
k2 = find(temprange==temp2);
k3 = find(temprange==temp3);
color1 = colormapinterp(k1,:,:); % find color based on index value
color2 = colormapinterp(k2,:,:);
color3= colormapinterp(k3,:,:);
figure
plot(x,y,'Color',color1)
hold on
plot(x,10*y,'Color',color2)
hold on
plot(x,5*y,'Color',color3)