fix: default random colour number generate one colour

Author: lachlangrose

LoopStructural/utils/__init__.py

@@ -36,3 +36,4 @@
 rng = np.random.default_rng()
 
 from ._surface import LoopIsosurfacer, surface_list
+from .colours import random_colour

LoopStructural/utils/colours.py

@@ -1,7 +1,7 @@
 from LoopStructural.utils import rng
 
 
-def random_colour(n: int, cmap='tab20'):
+def random_colour(n: int = 1, cmap='tab20'):
     """
     Generate a list of random colours