I’ve got a tobacco burst and transparent brown back with a ivroid binding. I think it looks really good. Tortoise binding with that combo wouldn’t be my jam, but to each his own.
If you have a low level of contrast, you risk it looking unintentionally weird, like it looks similar but not the same but you’re trying to force it. Imagine a vintage white guitar with ivroid, for example. With high contrast, it’s obvious you are going for an intentional look.