Change the icon_color comparing the state (numeric) of different entities

Hi everyone.

I have tried to change the icon color of an entity (in this case a sensor created in template.yaml), writting this in customize.yaml

sensor.prueba:
  friendly_name: PRUEBA 
  templates:
    icon_color: >
      if (state < 'input_number.referencia_prueba') return 'yellow';
      if (state > 'input_number.referencia_prueba') return 'orange';

The purpose is…
…comparing the entity sensor.prueba with the state of the numeric entity input_number.referencia_prueba.
…If sensor.prueba is above input_number.referencia_prueba, then the color of the icon of sensor.prueba has to change to orange
…If sensor.prueba is under input_number.referencia_prueba, then the color of the icon of sensor.prueba has to change to yellow.

With the code y pasted, the icon is always yellow. It doesnt matter if the state of sensor.prueba is above or under the state of input_number.referencia_prueba

Please, anyone who know what I am doing wrong??
Thanks in advance.

CREATING THE ENTITY (SENSOR)

CUSTOMIZING
1

CHECKING
2
4