From reading through the rules it seems to me this game is going to need tokens to represent red and yellow dice, as the game only comes with one each and from looking at it an investigator could quite easily be using more than one of each to complete a particular card.

Have I missed something obvious or is this going to be the case?

I think only one red and one yellow dice can be used at a time. If, for example, the red dice is stored on a spell, then no investigator can spend a unique item to gain a red dice in their dice pool, until the spell is used...

But I'm not sure anymore, an official answer is needed :)

Ah, that would make sense so the number of dice available in the game is an inherent limit on what can be rolled.

Certainly gets around the situation, although not sure that is clear from the rules.

The rules do state that you can use 1 or more common items etc on each roll, which implies that you could in theory be allowed to roll 2 red dice (dfor example), however, it may be that some items generate benefits not involving additional dice, so that the both rules could be valid.

I like "your" solution to the problem and avoids having to keep track of dice rolls etc, so may just pretend that is an official rule, even if it isn't!

I was thinking the yellow and red dice are limited and once stored or locked are not available until released.

Yes, I believe one of the previews mentioned that adventures or other things that lock the dice prevent those dice from being used ... as I recall it was referencing the choices players had to make on which adventures to try to complete.

Yeah dice get locked, some come into play and lock a dice. which can make things get tough quick.