Disable by default?

[savchenko]

Maybe I am missing something, but is there an option to disable plugin by default?
Calling css_color#disable() before file is loaded results in a bunch of errors:

Error detected while processing function css_color#disable:
line    1:
E121: Undefined variable: b:css_color_off
E15: Invalid expression: b:css_color_off | return | endif
line    2:
E121: Undefined variable: b:css_color_grp
E116: Invalid arguments for function len
E15: Invalid expression: len( b:css_color_grp ) | exe 'syn cluster colorableGroup rem
ove=' . join( b:css_color_grp, ',' ) | endif
line    3:
E216: No such group or event: CSSColor * <buffer>
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