def FindColorIn(r,g,b, xmin, xmax, ymin, ymax):
    image = ImageGrab.grab()
    for x in range(xmin, xmax):
        for y in range(ymin,ymax):
            px = image.getpixel((x, y))
            if px[0] == r and px[1] == g and px[2] == b:
                return x, y

def FindColor(r,g,b):
    image = ImageGrab.grab()
    size = image.size
    pos = FindColorIn(r,g,b, 1, size[0], 1, size[1])
    return pos

if ((X-X1)^2 + (Y-Y1)^2 + (Z-Z1)^2) <= (Tol^2) then
  ...

typedef struct {
   unsigned char r, g, b;
} RGB;

double ColourDistance(RGB e1, RGB e2)
{
  long rmean = ( (long)e1.r + (long)e2.r ) / 2;
  long r = (long)e1.r - (long)e2.r;
  long g = (long)e1.g - (long)e2.g;
  long b = (long)e1.b - (long)e2.b;
  return sqrt((((512+rmean)*r*r)>>8) + 4*g*g + (((767-rmean)*b*b)>>8));
}

def ColorDistance(rgb1,rgb2):
    '''d = {} distance between two colors(3)'''
    rm = 0.5*(rgb1[0]+rgb2[0])
    d = sum((2+rm,4,3-rm)*(rgb1-rgb2)**2)**0.5
    return d

>>> import numpy
>>> rgb1 = numpy.array([1,1,0])
>>> rgb2 = numpy.array([0,0,0])
>>> ColorDistance(rgb1,rgb2)
2.5495097567963922

if abs(px[0]- r) <= rtol and
   abs(px[1]- g) <= gtol and
   abs(px[2]- b) <= btol:
    return x, y

if px[0] == r and px[1] == g and px[2] == b:

if max(map(lambda a,b: abs(a-b), px, (r,g,b))) < tolerance:

def eq_with_tolerance(a, b, t):
    return a-t <= b <= a+t

def FindColorIn(r,g,b, xmin, xmax, ymin, ymax, tolerance=0):
    image = ImageGrab.grab()
    for x in range(xmin, xmax):
        for y in range(ymin,ymax):
            px = image.getpixel((x, y))
            if eq_with_tolerance(r, px[0], tolerance) and eq_with_tolerance(g, px[1], tolerance) and eq_with_tolerance(b, px[2], tolerance):
                return x, y

def pixelMatchesColor(x, y, expectedRGBColor, tolerance=0):
r, g, b = screenshot().getpixel((x, y))
exR, exG, exB = expectedRGBColor

return (abs(r - exR) <= tolerance) and (abs(g - exG) <= tolerance) and (abs(b - exB) <= tolerance)

def color_distance(rgb1, rgb2):
    rm = 0.5 * (rgb1[0] + rgb2[0])
    rd = ((2 + rm) * (rgb1[0] - rgb2[0])) ** 2
    gd = (4 * (rgb1[1] - rgb2[1])) ** 2
    bd = ((3 - rm) * (rgb1[2] - rgb2[2])) ** 2
    return (rd + gd + bd) ** 0.5