Cat colour and temperature

[Jux]

Siamese cats change colour according to temperature, the colder they are the darker their points.

We have a ginger mog whose undercoat is grey. She is looking very grubby at the moment as her undercoat is darker. It is not cold. She has been out sitting right in the sun. She should be much paler shouldn't she?

We don't know her antecedents as we got her from CPL, our vet speculated that she might have some Siamese in her, but if so, she's broken!

Any ideas what's going on with her undercoat?
Should I tell her she's got it wrong and if so, how do I break it to her? She's tiny for a full grown cat (she's 8 or 9 ) but fierce as anything!

Cheddar is a red Persian. She changes colour in the summer. Her coat is much lighter.

Pictures please of said cat.

My girl (a tabby tabster goes a bit greyer)

Is she moulting?.

Wow Cheddar looks like you’ve bleached her.

Here she is eating hair. It's really hard to get the grey to show on a photo (and I'm really shit at photography as I shake a lot).

She looks almost the same colour as Cheddar's summer coat.
Ps I have not bleached the Cheddar!

They are very similar, aren't they, Toddler? Ours is tiny and very delicate, little bones. She's about half the size of our tabby, who is admittedly quite a large cat. We have another who is a miniature puma; she's average size but still much bigger than our ginger.

My sibling pair, one black and one very dark charcoal tabby, have very pale silvery undercoats. They currently seem to be shedding a shade darker than they were a couple of months ago.