Sound symbolism is a linguistic concept that argues, despite Saussure’s (in)famous assertions to the contrary, that the link between signifier and signified is a necessary one. Roman Jakobson remains one of the few noteworthy exponents of the concept in the last century. One aspect of sound symbolism that particularly interested him was “coloured vowels,” that is, the “real” mental correlations of colours with vowels. Though this phenomenon remains inconclusive and under investigation, Jakobson maintained an unwavering belief in its veracity. However, in his discussions of the subject, Jakobson’s rhetoric conceals his assumption that this particular aspect of sound symbolism and its correlations are universal, that is, Jakobson believed, without saying so explicitly, that the perceived coloured values of vowels transcend borders and cultures. This paper demonstrates Jakobson’s rhetorical and allusive strategies to this end, including, for example, his recurring reference to Mallarmé.