This paragraph explains that color illustrations will be published in the online version of the journal free of cost, that is, you will not be charged for the color illustrations in the online version of the journal. However, if you want color illustrations in the print publication, you will have to pay some extra charges. Generally, it is not mandatory to pay these charges. You will probably receive an email from the journal after acceptance asking whether you would like the illustrations to be in color or in black and white. If you opt for black and white, you will not have to pay the additional charges. Most journals have both an online and a print version, and the same content appears in both. Unless otherwise specified, it is expected that if your paper is accepted, it will be published in both the online and print version.
I did not exactly understand this paragraph: "Color art will be reproduced in color in the online publication at no additional cost to the author. Color illustrations will also be considered for print publication; however, the author will be required to bear the full cost involved in color art reproduction. Please note that color reprints can only be ordered if print reproduction costs are paid" Does it mean its mandatory to pay once my paper is accepted or just when my paper is printed ? Is it mandatory also to print the paper? Please help