resistor-color: correct and clarify instructions (#1552)

The crates were associated with the wrong task numbers.
State that Debug will help with the second.

closes: #1499

Author: dvermd

exercises/concept/resistor-color/.docs/instructions.md

@@ -31,7 +31,10 @@ The goal of this exercise is to create a way:
 - to convert the numerical value into a string representing color
 - to list the different band colors
 
-For tasks number two and three, you will need external crates [`enum-iterator`](https://docs.rs/enum-iterator/1.1.1/enum_iterator/) and [`int-enum`](https://docs.rs/int-enum/0.4.0/int_enum/), which are included in this exercise's `Cargo.toml`. Be sure to check the crates' documentation to learn how to use them.
+For task number one, you will need the external crate [`int-enum`](https://docs.rs/int-enum/0.4.0/int_enum/) and for task number three, you'll need [`enum-iterator`](https://docs.rs/enum-iterator/1.1.1/enum_iterator/).
+They're both already included in this exercise's `Cargo.toml`. 
+Be sure to check the crates' documentation to learn how to use them.
+You can look into the default implementation of the Debug trait for Enums to complete task number two.
 
 Mnemonics map the colors to the numbers, that, when stored as an array, happen to map to their index in the array: Better Be Right Or Your Great Big Values Go Wrong.