There is no such thing as a SEUS Shaders mod.
What is generally referred to as the Shaders mod is more specifically known as karyonix's shader mod. This mod (and since 1.9 also Optifine) allow you to load what are commonly called "Shader packs".
Shader packs are the things that actually tell the GPU how to render things (and therefore determine how the things you see will actually look like). The shaders mod (and since 1.9 also Optifine) provide all the other stuff (like loading of shader packs and modification to the Minecraft code) that most people will never know of but which is never the less essential for shader packs to function.
SEUS is one example of a shader pack. Most shader packs work with both, Karyonix' Shader Mod and Optifine and can therefore also be used with the Replay Mod. Only shader packs that do not work with Optifine will not work with the Replay Mod. SEUS even recommends using Optifine in its installation instructions.