Fix f-string in color error message (#8639)

torchvision/utils.py

@@ -604,9 +604,9 @@ def _parse_colors(
  f"Number of colors must be equal or larger than the number of objects, but got {len(colors)} < {num_objects}."
  )
  elif not isinstance(colors, (tuple, str)):
- raise ValueError("`colors` must be a tuple or a string, or a list thereof, but got {colors}.")
+ raise ValueError(f"`colors` must be a tuple or a string, or a list thereof, but got {colors}.")
  elif isinstance(colors, tuple) and len(colors) != 3:
- raise ValueError("If passed as tuple, colors should be an RGB triplet, but got {colors}.")
+ raise ValueError(f"If passed as tuple, colors should be an RGB triplet, but got {colors}.")
  else: # colors specifies a single color for all objects
  colors = [colors] * num_objects