To tell if colored text is a link or just some characters that have a different color, move the mouse over the link. Normally, the cursor that shows you where the mouse is pointing is an arrow. But when you point near a link the arrow turns into a hand. If it is just colored test, like these words , the cursor doesn't turn into a hand. Thus, color and a little hand tell you what is or is not a text link.
Links can also be buttons or images on a page.
Usually, what the button or image does is obvious from the context or the look of the button or image. Here's a button and two images. To tell, move the mouse over the image and look for the tell-tale change of the cursor to a hand, just like with text links. For example, the following image is NOT a link. Links can also be embedded within images.