To load a pdb:
Select residues (p.69 VMD manual)
In the menu 'graphics'-'representations' select the molecule and 'create rep' to create a new object; then to select specific residues write in the box "selected atoms"
to select specific atoms in a residue and represent it in a different style:
then select i.e. CPK fot this new representation (this would show CPK for atom HD2 only belonging to residue 124).
To select residues within 7A from atom HD2 on residue 124:
How to smoothen trajectory