Red coloration on the radar indicates rain intensity. Heavy rain alone does not constitute a hazard to be avoided at all costs. The same applies to heavy(strong) landing/takeoff winds, heavy snow or ice, heavy weight, heavy anything, without considering other factors.
Experience and training come into play. If the red is accompanied by steep contouring or gradient, known CB activity, known tops which cannot be overflown by several thousand feet, known or depicted significant turbulence, lightning, stage of development other than dissipating and a strong sense of smell - as in this doesn't smell right - then by all means go around it, fuel permitting. Even a partial list would suffice in order to turn around or go around.
But if you have never flown through or over heavy rain, then I would be interested in knowing what your experience level is and where in the world have you operated.
Unless I have misunderstood your post, in which case, my apologies.
Piedmont1984