There is a Tolerance input intended to cope with a slight change in colour, eg RGB1=101,102,103 and RGB2=98,100,105 are deemed equal with a tolerance of +-5. If the runtime image is significantly different (eg antialiasing on text) then the Tolerance may not be effective.
Devising some sort of fuzzy match is certainly possible, but we don't offer anything at present. Once you get into fuzzy-matching you have to consider the effect of false-positives and false-negatives on your business process.