fix typo and markup

lib/PDL/Transform/Color.pm

@@ -786,7 +786,7 @@ color paths.  Autumn is similar to heat, but less garish.
 
 =item dop, dop1, dop2, dop3
 
-These are various presentations of signed infromation, originally
+These are various presentations of signed information, originally
 intended to display Doppler shift.  They are all quasi-photometric
 and split.
 
@@ -1656,8 +1656,8 @@ HSV is a stacked-cone system: iso-V surfaces are parallel to the
 bright faces of the RGB cube, so maximal bright saturation occurs when
 S=1 and V=1.  This means that output luminosity drops with saturation,
 but due to Helmholtz-Kolrausch effect (linking saturation to apparent
-brightness) the *perceived* brightness is less S-dependent: V follows
-total *apparent brightness* of the output, though output luminosity
+brightness) the I<perceived> brightness is less S-dependent: V follows
+total I<apparent brightness> of the output, though output luminosity
 drops with S.
 
 You can represent out-of-gamut values in either system, by using