Colored underline without affecting the default LaTeX style

Question

I would like to have a colored line. I tried the following:
documentclass[11pt,english]{article}
usepackage[T1]{fontenc}
usepackage[parfill]{parskip}
usepackage{color,soul}
setulcolor{red}

begin{document}

This word is underlined in black: underline{Zukunft}
This word is underlined in red: ul{Zukunft}

This word is underlined in black: underline{Gelegenheit}
This word is underlined in red: ul{Gelegenheit}

end{document}

The output is:

As one can see, the vertical spacing between the underlined word and the underline has increased when underlining the word "Zukunft" in red in comparison to one the underlined in black. Whereas, this is not the case with the word "Gelegenheit". Is this normal? If not, how to have a colored underline without compromising the default LaTeX settings?

Alan Munn · Accepted Answer

This is a design choice by soul: it sets a fixed underline depth based on all of the characters in the font, which then takes into account the characters with descenders (like gjpqy).
You can see the compromise in the other direction if you put two words side by side with underline, then the underlining itself doesn't line up. (Example 1) This is an aesthetic choice, fundamentally. With the soul underlining the underlining of such adjacent words is uniform (Example 2).
You can change the depth of the soul underline using the setuldepth command to match the height of words without descenders, but then you'd need to change it back to deal with words with descenders. (Example 3). A simple way to make this work is to  define a macro to set the depth according to the content every time. (Example 4).
documentclass{article}
usepackage{soul}
usepackage{xcolor}
usepackage{calc}
newcommand{myul}[1]{setuldepth{#1}ul{#1}}
setulcolor{red}
begin{document}

begin{enumerate}
item underline{abcdef}underline{gjpqy}
item ul{abcdef}ul{gjpqy}
item setuldepth{abc}ul{abcdef}ul{gjpqy}
item myul{abcdef}myul{gjpqy}
end{enumerate}

end{document}

Colored underline without affecting the default LaTeX style

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