colorstr() updates (#1909)

* W&B ImportError message fix

* colorstr() updates

* colorstr() updates

* colorstr() default to 'blue', 'bold'

* train: magenta

* train: blue

utils/plots.py

@@ -245,9 +245,9 @@ def plot_study_txt(path='study/', x=None):  # from utils.plots import *; plot_st
              'k.-', linewidth=2, markersize=8, alpha=.25, label='EfficientDet')
 
     ax2.grid()
+    ax2.set_yticks(np.arange(30, 60, 5))
     ax2.set_xlim(0, 30)
     ax2.set_ylim(29, 51)
-    ax2.set_yticks(np.arange(30, 55, 5))
     ax2.set_xlabel('GPU Speed (ms/img)')
     ax2.set_ylabel('COCO AP val')
     ax2.legend(loc='lower right')