opencv example in README leads to incorrect color identification with default settings

In the README example, an image file is opened using opencv, which will open the file in BGR. However, the `color_names.npz` dataset that comes with the repo is stored as RGB. Therefore if you use the example verbatim, you will get incorrect color identifications. Since `from_file.py` uses skimage.io instead of opencv, the only corrections needed are on the README, which are:

- replacing opencv calls with skimage.io calls
- removing any mention of needing color name files stored as BGR.

Start with the README example and compare it with from_file.py, which uses skimage.io. Check how color_names.npz is represented, then update the README so its image-loading example matches the dataset's RGB format and no longer mentions BGR color-name files.

Written by the indexing model from the issue text.