What the d-'s this yellow colour-changing bug?

I have never seen one before. On a broad bean leaf, sinking its beastly proboscis (I assume) in and sucking the lifeblood of my poor bean, insultingly wiggling its backside at me. Only one to be seen, from a cursory glance. I wondered if it might be an import from NZ, but unsure.

I'll get another picture when I can; it's now (6 hours later) completely changed, and is a sort of orange and black colour, like the tail end of a big fat ladybird larva, but AFAIK those are not sap suckers.

 

In its new colours:

 

Looks like a ladybird

 

That's what I thought, when I looked at the later images, but I have not seen a pupa before, only lots of larvae scurrying about all over the place (mostly harlequins, I am sorry to say).

I did not know they drink sap at this stage, which this item seems to be doing.

 

I thought maybe it was just attaching itself to the leaf.

 

If just one or two then whatever they are your bean plant won't be bothered and I would just keep an eye on them for the moment.
Never come across a sap sucking ladybird, but they do hang onto the leaves tightly and also suck the life out of aphids.
For more on ladybirds see UK Ladybird Survey | UK Beetle Recording

 

I am keeping it to see what it turns into.