If you are talking about the text decoration underline it is possible with some custom code but it is not an option in Webflow.
Anyhow most of the time this type of effect is not accomplished with text decoration.
You could instead go with the border bottom property. You will be able to set the colour of it separately from the text colour.
Just a side note as borders are changing the flow of the document try to avoid setting a different border size on hover otherwise you might end up with some shifting of surrounding elements.
But instead set the colour to transparent on normal state and your desired colour on hover.
Hope it make sens.