Patch:  changing color based on HP remaining in Vanilla Angband, v3.0.1.  This patch describes a slight code change which will change the player's color depending on remaining HP.  You must recompile for this change to take effect.

Files affected:  xtra1.c, cave.c

Instructions for implementation:

In xtra1.c, search for the text "redraw & (PR_HP", or just scroll to line 2766.  After this line, which should be a call to prt_hp in the function redraw_stuff, add this (at line 2770):
		/*
		* hack:  DSV:  redraw player, since the player's color
		*	now indicates approximate health
		*/
		lite_spot(p_ptr->py, p_ptr->px);


In cave.c, search for the text "a = r_ptr->x_attr;", or just scroll to line 984.  Replace this line with the following:
		/*  DSV:  I've chosen the following sequence of colors to indicate
				the player's current HP.  There are colors are left over, but I
				left them in this comment for easy reference, in the likely case
				that I decide to change the order of color changes.

			TERM_WHITE		100% of HP remaining
			TERM_L_UMBER	70-99% of HP remaining
			TERM_UMBER		50-69% of HP remaining
			TERM_SLATE		40-49% of HP remaining
			TERM_YELLOW		30-39% of HP remaining
			TERM_ORANGE		20-29% of HP remaining
			TERM_L_RED		10-19% of HP remaining
			TERM_RED		0-9% of HP remaining

			TERM_BLUE		-% of HP remaining
			TERM_L_BLUE		-% of HP remaining
			TERM_GREEN		-% of HP remaining
			TERM_L_GREEN	-% of HP remaining
			TERM_DARK		-% of HP remaining
			TERM_L_DARK		-% of HP remaining
			TERM_L_WHITE	-% of HP remaining
			TERM_VIOLET		-% of HP remaining
		*/

		switch(p_ptr->chp * 10 / p_ptr->mhp)
		{
		case 10:	a = TERM_WHITE  ;	break;
		case  9:
		case  8:
		case  7:	a = TERM_L_UMBER;	break;
		case  6:
		case  5:	a = TERM_UMBER  ;	break;
		case  4:	a = TERM_SLATE  ;	break;
		case  3:	a = TERM_YELLOW ;	break;
		case  2:	a = TERM_ORANGE ;	break;
		case  1:	a = TERM_L_RED  ;	break;
		default:	a = TERM_RED    ;	break;
		}

Recompile, and you're good to go.  It's true that the player's attribute in one of the txt files is now a useless field, but I'm not really concerned about that.

Give me feedback on a better color sequence, if you don't mind, at someog@mailcity.com.