like this ?
if this is the effect you want, open a photo editing program, like Photoshop, create a new image 512x512 pixels

with a transparent background, then "such as" draw a yellow circle, and save it in nametexture_D2.dds. the same circle as the white and save it in nametexture_I.dds.
with Notepad create a file.fpe
;Entity Spec
;Header
desc = circlelight
;AI
aiinit = appear1.fpi
aimain = default.fpi
aidestroy = disappear1.fpi
;Spawn
spawnmax = 0
spawndelay = 0
spawnqty = 0
;Orientation
model = meshbank\common\overlay.x
offx = 0
offy = 1
offz = 0
rotx = 0
roty = 0
rotz = 0
scale = 100
fixnewy = 0
collisionmode = 4
defaultstatic = 1
;Visualinfo
textured = nametexture_D2.dds
effect = effectbank\illuminationent\illuminationmap.fx
transparency = 4
;Identity Details
strength = 0
isweapon = 0
isammo = 0
isimmobile = 1
Put everything in a folder, in entitybank (texture and files together)
(I with photoshop export to png, then open paint.net and export to .dds)