JS: provide 'toString' method for Color4d
JS: provide 'toString' method for Color4d

Allows the tag colours to be shown in the Property Viewer.

Signed-off-by: Harry King <409587b9e6671aa0763646191d292852dc49a658@gmail.com>

jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim,jaamsim/jaamsim