In Excel 2007, goto Insert/Shape and pick a shape. Colour it and enter whatever text you want. Then right click on the shape and insert a hyperlink
A few tips with shapes..
If you want to easily position the shape with cells, hold down Alt when you move the shape and it will lock to the cell. If you don't want the shape to move or resize with rows/columns, right click the shape, select size and properties and choose the setting which works best.