I'm not sure how to interpreting that measure; is that one large dashed slur, it three short slurs?

If you want a dashed slur, use \slurDashed:

\slurDashed
c''16( b' a' g' a' b') |

If you need more control of the dashes you can use \slurDashPattern (with a numbers for the dash ratio, and a number for the dash period):

\slurDashPattern #0.5 #5
c''16( b' a' g' a' b') |

For more options and details about dashed and dotted slurs, see:
https://lilypond.org/doc/v2.24/Documentation/notation/expressive-marks-as-curves

To simply change to colour of slurs use \override Slur.color (and specify the colour in hexadecimal):

\override Slur.color = "#888888"
c''16( b') a'( g') a'( b') |

I'm not sure how to interpreting that measure; is that one large dashed slur, it three short slurs?

If you want a dashed slur, use \slurDashed:

 \slurDashed c''16( b' a' g' a' b') | 

If you need more control of the dashes you can use \slurDashPattern (with a numbers for the dash ratio, and a number for the dash period):

 \slurDashPattern #0.5 #5 c''16( b' a' g' a' b') | 

For more options and details about dashed and dotted slurs, see:
https://lilypond.org/doc/v2.24/Documentation/notation/expressive-marks-as-curves

To simply change to colour of slurs use \override Slur.color (and specify the colour in hexadecimal):

 \override Slur.color = "#888888" c''16( b') a'( g') a'( b') | 

I'm not sure how to interpreting that measure; is that one large dashed slur, it three short slurs?

If you want a dashed slur, use \slurDashed:

 \slurDashed c''16( b' a' g' a' b') | 

If you need more control of the dashes you can use \slurDashPattern (with a numbers for the dash ratio, and a number for the dash period):

 \slurDashPattern #0.5 #5 c''16( b' a' g' a' b') | 

For more options and details about dashed and dotted slurs, see:
https://lilypond.org/doc/v2.24/Documentation/notation/expressive-marks-as-curves

To simply change to colour of slurs use \override Slur.color (and specify the colour in hexadecimal):

 \override Slur.color = "#888888" c''16( b') a'( g') a'( b') | 

I'm not sure how to interpreting that measure; is that one large dashed slur, it three short slurs?

If you want a dashed slur, use \slurDashed:

\slurDashed
c''16( b' a' g' a' b') |

If you need more control of the dashes you can use \slurDashPattern (with a numbers for the dash ratio, and a number for the dash period):

\slurDashPattern #0.5 #5
c''16( b' a' g' a' b') |

For more options and details about dashed and dotted slurs, see:
https://lilypond.org/doc/v2.24/Documentation/notation/expressive-marks-as-curves

To simply change to colour of slurs use \override Slur.color (and specify the colour in hexadecimal):

\override Slur.color = "#888888"
c''16( b') a'( g') a'( b') |