You can use the following snippet:
tr td:first-child {text-decoration: underline;}
tr td:last-child {color: red;}
Using the following pseudo classes:
:first-child means "select this element if it is the first child of its parent".
:last-child means "select this element if it is the last child of its parent".
Only element nodes (HTML tags) are affected, these pseudo-classes ignore text nodes.