A lot of people use the small letter as the normal trait and the Capital one has the recessive gene.

I find it easier to use the "n" as the normal or wildtype trait. and use a Capital for the dominant/codominant genes. And use a small letter if it's recessive.

That way you get this :
Pastel : Pn
Super Pastel : PP
Cinnamon : Cn
Super Cinnamon CC
Pewter : PnCn
Ghost : GG
Het Ghost : Gn
Pewter Ghost : PnCnGG

If you want to breed a Pastel to a Cinnamon, then you do this :
Pastel : Pnnn
Cinnamon : nnCn

and you get

Code:
Punnett Square

Pnnn x nnCn

        Pn	Pn	nn	nn
nC	PnCn	PnCn	nnCn	nnCn
nn	Pnnn	Pnnn	nnnn	nnnn
nC	PnCn	PnCn	nnCn	nnCn
nn	Pnnn	Pnnn	nnnn	nnnn


Genotype Frequencies: 
PnCn:    4 ( 25% ) Pewter
Pnnn:    4 ( 25% ) Pastel
nnCn:    4 ( 25% ) Cinnamon
nnnn:    4 ( 25% ) Normal
Using the first method would have also work but I think it's harder to read.
Code:
Ppcc x ppCc

        Pc	Pc	pc	pc
pC	PpCc	PpCc	ppCc	ppCc
pc	Ppcc	Ppcc	ppcc	ppcc
pC	PpCc	PpCc	ppCc	ppCc
pc	Ppcc	Ppcc	ppcc	ppcc


Genotype Frequencies: 
PpCc:    4 ( 25% ) Pewter
Ppcc:    4 ( 25% ) Pastel
ppCc:    4 ( 25% ) Cinnamon
ppcc:    4 ( 25% ) Normal (the genotype to read it get confusing I think)