text: Title: Matplotlib warning about color usage in Datasaurus
  Body: **Describe the bug**
  the datasaurus function used to demonstrate Anscombe's quartet is isssuiing the following warning
  
  WARNING:matplotlib.axes._axes:*c* argument looks like a single numeric RGB or RGBA sequence, which should be avoided as value-mapping will have precedence in case its length matches with *x* & *y*.  Please use the *color* keyword-argument or provide a 2D array with a single row if you intend to specify the same RGB or RGBA value for all points.
  
  **To Reproduce**
  
  ```python
  from yellowbrick import datasaurus
  datasaurus()
  ```
  
  **Dataset**
  
  **Expected behavior**
  Produce the image without warnings
  
  
  **Desktop (please complete the following information):**
   - OS: [e.g. macOS] Google Colab
   - Python Version [e.g. 2.7, 3.6, miniconda] 3.8.10
   - Yellowbrick Version [e.g. 0.7] 1.5
  
  
  