Developing a locomotive scheme can be tricky...I took the easy way I out and copied a prototype example.  Since the Penn Lake Railway is partially owned by the Delaware and Hudson, it wasn't much of a stretch to use elements of the D&H's first diesel scheme.  In fact for several units, I just bought D&H units and replaced Delaware & Hudson with Penn Lake

For other units, while changing the body color, I still used a combination of D&H decals and custom lettering

Penn Lakes cabooses are also patterned after D&H's bay window ones.  Some modifications to an Athearn caboose, a set of D&H decals and custom lettering, and has some snazzy looking cabooses.

PL hopper fleet uses typical lettering schemes.    The big coal hoppers are Bowser data only kits with custom lettering.

PL's yellow ore hoppers are a play on the D&H's yellow ilmenite cars, but I added a red end panel.

Nick