Even if we define a system perfectly, it will be foiled by other factors. Frequently two pictures of roses from two sources will show roses that bear little resemblence to each other. To some extent the disparity is in the color reproduction in the print medium, but growing conditions can play an important role as well. The sun that the rose so dearly loves to blossom beautifully can bleach and fade the blossom, especially in punishing heat. Alternatively, it can darken the blossom as is the case with roses that are heavily influenced by China Roses.
Moisture can change flower color as well.
In short, no rose will look exactly as you expect it to, but hopefully this guide will produce pretty good first-guesses about rose color. So if you seek a reddish rose check also under scarlet, and crimson. If you seek a pink rose, check the colors that contain the word pink and look also under the color names rose and cerise and perhaps lilac. If you want a yellow rose, then look into buff and check out primrose, investigate pale apricot, and consider gold before settling for yellow or chrome yellow. Roses that have more than one color will be the hardest to deal with, but there are some patterns.