In Australia, usually filing your trademark in black and white or greyscale is the best approach, as upon registration your mark is protected for all colours.
However, sometimes colour plays a significant role in your branding and it may be appropriate to file your mark in colour. For instance, if you always use a colour or particular colour combination for your trademark and corporate branding. Although, to ensure you secure as broad as protection as possible, you may wish to consider filing in both greyscale and colour.
Of course, sometimes a colour is your brand, so actually filing a colour mark is what you require.
If your mark is not particularly distinctive a colour endorsement may assist in making your trademark more registrable.
So, whether it is appropriate to file your trademark in colour, will depend on your particular circumstances.
Of course, if you would like help in deciding whether you should file your trade mark in colour or greyscale, please contact me.
Please note these brief and general comments are in respect of Australian trademarks, other countries take different approaches. Of course, if you would like further information in respect of protection for your trademark overseas,
please contact me.