Open your save in Gibbed.
Click over to "Raw"-> Player -> Appearance -> Headmorph
Click the [...] button to the right of (Collection) next to Scalar Parameters to open up a 2nd window.
A list of useful values and what they mean:
HED_Blush_Scalar - Controls blush transparency. Zero will be nothing, one will be quite heavy. Anything higher and you're probably heading into clown territory, depending on what color your blush is (more on color selection later.)
HED_Addn_SPwr_Lips_Scalar - Together these two control lip shine. For example in the picture above I have the first set at "10" and the second set at "100". Zero for both means no extra shine.
HED_Addn_Blowout_Scalar - How dark custom eyebrows are saturated with color. Default femshep won't be affected because her eyebrows are painted on her face, but this can be used on any character creator femshep. "0.5" will be very thin brows - "1.5" will be very dark.
HED_Lips_Tint_Scalar - Controls lip color transparency. Same as blush, zero is nothing - one is about normal and anything higher is subjective.
HED_EyeShadow_Tint_Scalar - eyeliner heaviness
HED_Brow_Tint_Scalar - eyeshadow heaviness
In ME3 both will be much lighter than in previous games, and the eyeliner is less defined. The ME3_legacy_makeupmask.tpf I have in my default femshep download will return it to its previous appearance. The texture overhaul also includes a modified version.
HED_SPwr_Scalar - How much light Shepard's face emits, for lack of a better descriptor. Higher values will make her glow more.
Hightlight1Intensity - How much hair highlight color 1 shows/shininess
Hightlight2Intensity - How much hair highlight color 2 shows/shininess
Vector Parameters (aka color values)
ME3 Gibbed has a user friendly color interface that comes up in the Appearance tab. Click the value you want to edit and the Change Color button to bring up the color wheel.
HED_Blush_Vector - Blush color
SkinTone - Skin Color
EYE_White_Colour_Vector - Eye color (area around the iris)
EYE_Iris_Colour_Vector - Eye color (iris)
HED_Hair_Colour_Vector - Base hair color
HED_Addn_Colour_Vector - Eyebrow color
HED_Lips_Tint_Vector - Lipstick color
HED_EyeShadow_Tint_Vector - Eyeliner color
HED_Brow_Tint_Vector - Eyeshadow color
Highlight1Color - Hair highlight color
Highlight2Color - 2nd hair highlight color
The old way...also useful for transferring values from ME2 save editor.
Opening "Vector Parameters" (Collection) in the "Raw" tab will bring up the RGB number values.
This is where you specify which textures (such as diffuse, spec, and normal maps) are used on Shepard. A list of mined values is HERE.
Diffuse: The visible flat texture most people think of when they are thinking about game textures
Spec: Controls how light reflects and interacts with an object
Normal: Adds depth and surface detail
Mask: Looks black and white, determines where color is visible or transparent, like on eyelashes. Think of it like a stencil.
HED_Scalp_Diff - Scalp diffuse
HED_Scalp_Norm - Scalp normal map (also known as a bump map)
HAIR_Diff - Hair diffuse
HED_Diff - Face diffuse
HED_Lash_Diff - Eyelash mask
HED_Norm - Face normal map
HED_Makeup_Mask - Makeup mask
HAIR_Mask - Hair mask
HED_Brow - Eyebrow mask
For a nice visual guide to makeup, color, and eyebrows check out this blog by Corora: link