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Fountain pens replaced standard metal pens because they were easier to use and were less messy. After years of improvements (and after appearance of ballpoint pens which are even easier to use) they became a sort of status symbol. Read more about history of fountain pen.
Mechanical pencils are also old invention dating even from 16th century. First ones were relatively simple mechanisms, only to become more complicated with time. Today we have mechanical pencils which can write and draw very precisely.
Compared with other art mediums, colored pencil is relatively new. It appeared at the beginning of the 20th century. But that doesn’t mean it is any less worthy especially when combined with other mediums. Here you can read more about colored pencil history.
Highlighters are useful tools: you can use them to mark dates on a calendar, parts of the relevant text in a book or any other use where you need highlight something on paper. Thy influenced our lives so much that we can even find them in some computer programs. Read more about history of highlighters.