They might make it past that first line of defense. For the second, you'll need some picture frames, a level, and a protractor that can do increments of less than a degree.
Cueball is inviting Knit Cap into his newly repainted residence. Knit Cap is a graphic designer and he simply can't enter because of the color scheme used. The caption explains that if you paint each wall a slightly different shade of off-white, a graphic designer will be so repulsed that they are physically unable to enter the room. This is analogous with a specific bit of vampire lore: Vampires cannot enter a dwelling uninvited.
Being presented with visual information that is just not quite right is known to cause feelings of unease and revulsion, particularly when presented with CGI human faces, a concept known as the uncanny valley. This may not be strictly an attempt to annoy, but it portrays a similar vibe to those which are.
In the title text, it mentions a contingency against the designer managing to actually overcome this disgust. In this case, Cueball sets up a second way to troll his graphic designer friend using some picture frames, a level, and a protractor that can measure increments of less than a degree. Cueball can then skew his picture frames by an extremely small amount, noticeable only to the designer friend, to disgust him even further — similar to the effect of bad kerning. This could thus be applied as with the use of crosses or garlic, which vampires are famously repulsed by.
Although the window ledges are slightly inclined, falling subtly from left to right, it is unlikely this is a deliberate aspect of the room so much as a side-effect of Randall's imprecise stick-figure drawing style.
Colors
True to the comic's joke, Randall has actually colored each segment of the comic differently to each other, even though normal persons would just perceive all walls as slightly gray (off-white). The hexadecimal color codes are:
- Floor: #FFFFFF [White]
- Ceiling: #F3F7F8 [Light Grayish Cyan]
- Walls (left-to-right)
- #F2F0EE [Light Grayish Orange]
- #F3F4F2 [Light Grayish Green]
- #F2F3F4 [Light Grayish Blue]
- #F3F2F4 [Light Grayish Violet]
- Door: #F1F3F1 [Light Grayish Lime Green]
- Left window frame/ledge: #F2EEF2 [Light Grayish Magenta]
- Right window frame/ledge: #F3F3F1 [Light Grayish Yellow]
- Box seat top: #EEF1EC [Light Grayish Green]
- Box seat front: #F2EEF0 [Light Grayish Pink]
- Rug outer ring: #F0F2F1 [Light Grayish Cyan - Lime Green]
- Rug inner panel: #F0EFF1 [Light Grayish Violet]