Bug: black lines on graphs on black background

### What Happened?

It is possible to have Matlab in dark mode. When the examples run, they plot some of the lines on the graphs in black, so they can't be seen. 

### Error messages

```shell

```

### How Can We Reproduce?

To see this, set Matlab to dark mode and run one the IVP 1D, 2D, 3D example.

### Operating System

Windows

### Release Version

1.4 (Default)

### MATLAB Version

R2025b