One utility of blue/red is that it applies to other contexts that would cause similar "poison" effects as well. Some type systems allow for validated vs. unval

One utility of blue/red is that it applies to other contexts that would cause similar "poison" effects as well. Some type systems allow for validated vs. unvalidated data. And then all of a sudden you have a creeping concern that half your functions talk about char* and half your functions talk about String (or, perhaps, a heterogeneous collection of strings: userid and telephone number and the like). Suddenly the code on the outside of the validation boundary can't use the code on the inside without addressing the question of whether their data is valid.