Enumerations are used to represent symbolic values, or sometimes bit fields. They are not supposed to be used in arithmetic contexts.
Additionally, even though comparing them with integer numbers can make sense (for instance, to test if an enum lies with a certain range),
comparing them with floating point numbers does not (and is deprecated since C++20).
There are other restrictions related to the use of enums, see for instance S2753.
Noncompliant code example
enum { COLOUR_0, COLOUR_1, COLOUR_2, COLOUR_COUNT } colour;
if ( COLOUR_0 == colour ) { ... }
if ( ( COLOUR_0 + COLOUR_1 ) == colour ) { ... } // Noncompliant, arithmetic used
if ( colour < COLOUR_COUNT ) { ... }
if ( colour > 3.14 ) { ... } // Noncompliant, comparison with float
