我用固定的边界条件和消耗项解决了二维几何中的扩散方程。如何在色彩图中添加一个新颜色（或2D图形上的虚线），指定（x-y）图形中某个化学浓度水平？例如，在此代码中，我的色彩图从暗红色变为深蓝色，因为解决方案从顶部的155变为底部的24，我如何为色彩图添加不同的颜色，显示2D图上的位置解决方案18岁？
c = 1e-1;
a = 0;
f = char('-22222*u./(2.2+u)');
d = 1;
xmin=0;xmax=0.575;ymin=0;ymax=0.05315;ymax2=0.073;
gdm = [3;4;xmin;xmax;xmax;xmin;ymax;ymax2;ymin;ymin];
g = decsg(gdm, 'S1', ('S1')');
hmax = .1; % element size
[p, e, t] = initmesh(g, 'Hmax', hmax);
[p,e,t] = refinemesh(g,p,e,t);
[p,e,t] = refinemesh(g,p,e,t);
[p,e,t] = refinemesh(g,p,e,t);
[p,e,t] = refinemesh(g,p,e,t);
[p,e,t] = refinemesh(g,p,e,t);
% Create a pde entity for a PDE with a single dependent variable
numberOfPDE = 1;
pb = pde(numberOfPDE);
% Create a geometry entity
pg = pdeGeometryFromEdges(g);
bc1 = pdeBoundaryConditions(pg.Edges(1),'u',155);
bc2 = pdeBoundaryConditions(pg.Edges(2),'u',51);
bc3 = pdeBoundaryConditions(pg.Edges(3),'u',24);
bc4 = pdeBoundaryConditions(pg.Edges(4),'g',0);
pb.BoundaryConditions = [bc1,bc2,bc3,bc4];
u = pdenonlin(pb,p,e,t,c,a,f, 'jacobian', 'lumped');
figure;
pdeplot(p, e, t, 'xydata', u, 'contour', 'on', 'colormap', 'jet');
title 'Chemical Diffusion, Steady State Solution'
xlabel 'X-coordinate, meters'
ylabel 'Y-coordinate, meters'