Decorative as in not having a specific descriptive function which obeys acquired rules of construction (“compare European sculptures based upon the ‘muscle’ with African ones based upon the medium” Matisse paraphrased) Did Picasso ever escape this approach or rather moved to the extreme end of the same axis…? , not decorative as in not just a ‘streamlined’ arrangement of colour and pattern (Louis Valtat a minor example, though if you want to start a sword fight with anyone – compare with Derain?)- this is the notion of colours just existing in their own right with no “pressure” (witness recent discussions on Abcrit) , decorative as in a full synthesis of perceived – real, fluid- space translated into painted space -(absorbing and extending the lesson of Cézanne and NOT coming up with cubism which took his vernacular and returned it to point 1 – see above), not decorative as in a systematic synthetic formatting (which is where twentieth century modernism went). I think it’s such a complex word to explore and may well continue to be redefined. Matisse saw colour as a “force” and used colours which “collide” into one another, however his painting journey to get to the late 40s (for it was a wilfully investigative one) was delightfully meandering and lit up so many intriguing side roads (for so many others to wander down).