For more information on the Hypershade, see Hypershade window.
Just like in the Node Editor, shader graphs in the Hypershade have ports and connection lines that are represented by different colors to denote the attribute type for the input or output, for example, integer, string, boolean and so forth. The connection line takes on the color of the output.
The Hypershade and the Node Editor share the same port and connection line colors. To change the default colors, select Windows > Settings/Preferences > Color Settings and adjust the colors in the Node Editor > Attribute Types section.