色散是指不同频率的波具有不同的群速度。数值色散理解起来比较抽象，在知乎上看到一个很好的评论留言，分享一下：

这个回答比较精辟，讲了分辨率和精度的关系。精度对应耗散，分辨率对应色散。最近在写一个程序遇到相关的问题，后面回头来补一下这个地方的算例图。

另一个回答在这里：https://www.cfd-online.com/Forums/main/207906-difference-between-diffusion-dissipation-dispersion-physical-numerical.html

我们求解无色散、无耗散的偏微分方程时，即使方程本身没有色散和耗散，数值方法的使用也会使得出现耗散和色散。我们可以通过选取减小这些影响的数值方法。

If you solve a non-dissipative and non-dispersive pde with a numerical scheme, you want the numerical solutions to be non-dissipative and non-dispersive. Sadly this is not possible since numerical solutions will exhibit these behaviours even if the exact solution does not. Then we say that the numerical scheme is dissipative and/or dispersive and the interesting thing is to design schemes which atleast minimize these effects which are not present in the exact solution.