By default, table borders look like this:
Note that no cellspacing or cellpadding has been applied.

cellspacing controls the gaps a bit but the border has a beveled appearance by default

You can fake a coloured border
You can fake a coloured border by adding it as a background to the table
Then making the cells inside the table white with a bgcolor attribute
This is, by far, the most compatable method of adding coloured borders to a table.

cellpadding give the text some space to breath

And, of course, you can make your table a garish nightmare
by recolouring each cell a different colour.

A hr element can be used to divide up the page. It doesn't seem to take colours from font tags:

However, this was not the intended method of adding coloured borders to tables. Instead, the frame and rules attributes can be used to add a variety of coloured borders to tables.

Unfortunately, support for these techniques is patchy at best. Some browsers ignore the bordercolor attribute, but render the borders correctly, other browsers respect the bordercolor attribute, but ignore the frame and rules attributes. If you absolutely had to use this technique, define the colour of the border twice, one with a font tag wrapped around the whole table and a second time with a bordercolor attribute directly on the table itself.

no frame or rules attributes
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

The frame attribute has the following values:
void (none - default)
above
below
hsides
vsides
lhs
rhs
box
border

Frame void
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame above
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame below
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame hsides
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame vsides
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame lhs
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame rhs
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame box
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Frame border
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

The rules attribute has the following values:
none (default)
groups (for example thead or tbody)
rows
cols
all

Rules none
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Rules groups
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Rules rows
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Rules cols
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14

Rules all
Table head Table header Nunc tincidunt gravida Ut finibus id
Table body table header 0.25 0.66 1.25
Donec ac blandit dui 0.01 0.22 1.11
Quisque varius 0.58 2.88 5.78
Table foot table header 0.84 3.76 8.14