**Table 4:** Parameters of the colour gradients distributions.
Grad.	N	Min	Max	Mean	$\sigma$	Skew	$\sigma_{\rm err}$
$\Delta _{UB}$	41	-0.08	-0.25	-0.157	.042	- $0.52\pm .6$	.027
$\Delta _{BV}$	53	-0.02	-0.12	-0.066	.022	- $0.32\pm .5$	.013
$\Delta_{BR}$	43	-0.03	-0.13	-0.082	.028	- $0.27\pm .6$	.015
$\Delta_{VI}$	47	-0.03	-0.16	-0.061	.036	- $1.12\pm .6$	.021
$\Delta _{VJ}$	53	-0.01	-0.35	-0.136	.092	- $1.15\pm .5$	.032
$\Delta _{VK}$	53	-0.07	-0.52	-0.227	.112	- $1.48\pm .5$	.035
$\Delta_{JH}$	54	-0.01	-0.11	-0.054	.026	- $0.51\pm .5$	.017
$\Delta_{JK}$	54	-0.04	-0.17	-0.093	.033	- $0.51\pm .5$	.017

(1) Gradient $\Delta_{AB}$ of colour A-B. (2) Number N of objects. (3) Minimum (one value in V-I rejected). (4) Maximum. Both are averages of two extreme values (NGC 5866 rejected). (5) Mean. (6) Standard deviation $\sigma$ . (7) Skewness and its probable error from the formula in Numerical Recipes (Press et al. 1992). (8) Probable errors of measured gradients $\sigma_{\rm err}$ . No rejections are made for the calculation of the parameters in Cols. (5)-(7).

Source LaTeX | All tables | In the text

	1 Introduction
	2 Collecting the gradients
	3 Properties of colour gradients
	4 Simulated datasets of colour gradients
	5 Concluding summary
	References